Input: Selective laser melting (SLM) is an additive manufacturing process in which multiple, successive layers of metal powders are heated via laser in order to build a part.

Selective laser melting

SLM

additive manufacturing process

metal powders

laser

build


Input: Modeling of SLM requires consideration of the complex interaction between heat transfer and solid mechanics.

Modeling

SLM

heat transfer


Input: The present work describes the authors initial efforts to validate their first generation model, as described in Hodge et al.

model

as

al


Input: Additionally, results of various perturbations of the process parameters and modeling strategies are discussed.

process parameters

modeling


Input: Density, surface roughness and mechanical properties of printed AlSi10Mg parts depend strongly on the manufacturing process of the used powder.

Density

surface roughness

mechanical properties

powder

manufacturing process


Input: The plasma atomized powder used in this study enables higher scanning speeds and thus a more efficient LPBF process than gas atomized powder.

plasma

atomized

scanning speeds

LPBF

gas atomized


Input: The measurement of the laser absorption is very sensitive to variations of the powder and reveals a clear correlation to the final part densities.

measurement

laser

absorption

variations

powder


Input: The present paper aims to generate a deeper understanding of the influence of powder properties on the final parts manufactured by metal LPBF processes at constant parameter settings, except the hatch scanning speed.

powder

metal

manufactured

parameter

LPBF

scanning speed


Input: This issue was considered using four different AlSi10Mg powders.In addition to particle properties, such as particle size distribution and morphology, typical properties of the powder feedstock like bulk and tapped density, Hausner-Ratio, flowability and laser absorption were measured.

as

particle

distribution

morphology

properties

absorption

powder feedstock

density

laser


Input: Furthermore, the in situ density of the powder layers applied during the LPBF process were analyzed.

in situ

density

powder

LPBF


Input: A comparison of the surface quality, part density and mechanical properties of AlSi10Mg parts produced by LPBF, using different particle size distributions and morphologies, has been conducted.

surface quality

density

mechanical properties

particle size distributions

morphologies

LPBF


Input: Within the processing experiments, the laser scanning speed was varied in order to achieve the most economical manufacturing of parts with a density > 99.2% .Following this comparison, it was found that the manufacturing process of the powder and therefore the particle morphology has the biggest impact on the part density and surface quality.

laser

manufacturing

manufacturing process

density

density

powder

particle

morphology

impact

surface quality


Input: The considered plasma atomized powder could be processed at a higher scanning speed without a significant decrease in mechanical properties or part density.

plasma

mechanical properties

atomized

be

scanning speed

density


Input: Generally, it was shown that higher densities of the powder layer result in higher part densities.

powder

layer


Input: However, the layer densities for powders which show almost the same bulk density can differ significantly and do not reach the regarding bulk density value.

layer

powders

density

density


Input: Therefore it can be stated that the layer density is not only affected by the bulk density.

be

layer

density

density


Input: In terms of surface quality, the investigated plasma atomized powder provides a significantly lower surface roughness.Moreover, it was found that the measurement of the laser absorption shows a strong correlation to the achievable part densities.

surface quality

plasma

surface

absorption

atomized

laser

measurement


Input: In contrast to the other methods performed, it was the only measurement that is very sensitive even to small variations of the powder and enables an unequivocal differentiation of the examined powders.

measurement

variations

powder

powders


Input: Additive Manufacturing offers many potential benefits including reduced tooling costs and increased geometric freedom.

Additive Manufacturing

tooling costs

geometric freedom


Input: However, the surface quality of the parts is typically below that of conventionally-processed materials.

surface quality

materials


Input: This paper evaluates a new chemical post-processing method to reduce the roughness of laser-sintered Nylon 12 components.

post-processing

roughness

Nylon

components


Input: This process is called the PUSh™ process.

process

process


Input: The treatment reduced the surface roughness of sample parts from 18 μm to 5 μm Ra and largely eliminated roughness with length scales below 500 μm.

surface roughness

roughness

sample

length scales


Input: Treatment did not affect the flexural modulus, flexural strength, or dimensions of 3.2 mm thick bending specimens, but it did significantly impact the mechanical properties of thin tensile specimens that are one to eight layers thick.

flexural strength

dimensions

mm

bending

impact

mechanical properties

tensile specimens


Input: The post processing reduced the breaking force of the samples, but it increased the ultimate tensile strength and elongation at break.

post processing

force

samples

ultimate tensile strength

elongation


Input: The impact was largest on the thinnest parts.

impact


Input: Significant sample shrinkage (12–20%) and weight gain (3.7–7%) from treatment was also observed in the tensile specimens.

sample

weight gain

tensile specimens


Input: The results show that the PUSh™ process dramatically increases surface smoothness and elongation at break in thin specimens.

process

surface

smoothness

elongation


Input: It decreases the surface strength, but effects are negligible in larger samples.

surface

samples

strength


Input: Selective laser melting (SLM) has emerged as one of the primary metal additive manufacturing technologies used for many applications in various industries such as medical and aerospace sectors.

Selective laser melting

SLM

metal additive manufacturing

as

as

industries

aerospace


Input: However, defects such as part distortion and delamination resulted from process-induced residual stresses are still one of the key challenges that hinder widespread adoptions of SLM.

defects

distortion

delamination

as

residual stresses

SLM


Input: For process parameters, the laser beam scanning path will affect the thermomechanical behaviors of the build part, and thus, altering the scanning pattern may be a possible strategy to reduce residual stresses and deformations through influencing the heat intensity input distributions.

process parameters

laser beam

thermomechanical

deformations

heat

distributions

build

scanning pattern

be

residual stresses


Input: In this study, a 3D sequentially coupled finite element (FE) model was developed to investigate the thermomechanical responses in the SLM process.

finite element

model

thermomechanical

process

FE

SLM


Input: The model was applied to test different scanning strategies and evaluate their effects on part temperature, stress and deformation.

model

scanning strategies

deformation

temperature

stress


Input: The major results are summarized as follows.

as


Input: (1) Among all cases tested, the out-in scanning pattern has the maximum stresses along the X and Y directions; while the 45° inclined line scanning may reduce residual stresses in both directions.

scanning pattern

Y

scanning

residual stresses


Input: (2) Large directional stress differences can be generated by the horizontal line scanning strategy.

stress

be

scanning strategy


Input: (3) X and Y directional stress concentrations are shown around the edge of the deposited layers and the interface between the deposited layers and the substrate for all cases.

Y

substrate

stress concentrations

deposited layers

deposited layers

interface


Input: (4) The 45° inclined line scanning case also has a smaller build direction deformation than other cases.

scanning

build direction


Input: Directed Energy Deposition (DED) was used to form a Stainless Steel AISI 316 L steel block component on a Mild Steel S235JR substrate.

Directed Energy Deposition

DED

Stainless Steel

steel

Mild Steel

substrate

component


Input: Porosity, density, and defect were characterised at 4 localities within the DED component by microscopy and x-ray tomography.

Porosity

density

defect

DED

component

microscopy

x-ray tomography


Input: Three-dimensional (3D) reconstruction of the x-ray tomographic image sequences focused at select porosities is presented.

Three-dimensional

reconstruction

image

x-ray

porosities


Input: The element composition and Vickers microhardness measurements were taken at the fusion lines and track body locations to characterise the differences in materials and mechanical properties at the 2 locations.

element

composition

microhardness

fusion

materials

mechanical properties


Input: Lastly, an element mapping analysis was conducted to determine the solidification mode for the DED component.

element

solidification

DED

component


Input: Sources for defects were proposed based on the characteristics of the porosity analysis and conclusions were made about the solidification behaviour of the DED component.

defects

solidification

porosity

DED

component


Input: Laser powder bed fusion (LPBF) was applied in this study to produce a prototype of a miniaturized catalytic burner (CAB), which is a key component of high-temperature polymer electrolyte fuel cells.

Laser powder bed fusion

LPBF

prototype

catalytic burner

component

polymer electrolyte fuel cells


Input: This prototype was characterized by its complex design with numerous channels, chambers, and thin walls.

prototype

design


Input: The test samples and CAB prototype were made of a heat-resistant, anti-corrodible steel called ``Alloy 800H'' (1.4876), a material that poses problems for welding operations and especially for the LPBF process due to its strong susceptibility to hot cracking and spatters.

samples

prototype

hot cracking

steel

Alloy

material

welding

LPBF

susceptibility


Input: The effects of LPBF parameter variation on preliminary test samples were investigated by nano-focus Computed Tomography (CT) and Optical microscopy to clarify the internal structure and defects for further LPBF process optimization.

LPBF

LPBF

variation

samples

defects

optimization

Computed Tomography

Optical microscopy

CT

internal structure


Input: Mössbauer spectroscopy points out that LPBF process does not lead to either local phase separation nor oxidation of steel, which is critical factor for use of CAB at high temperatures.

spectroscopy

phase

LPBF

oxidation

lead

steel

critical factor

temperatures


Input: The sufficient LPBF parameter sets were used to manufacture the CAB prototype, which was examined by micro-CT and optics as well.

LPBF

manufacture

prototype

micro-CT

optics

as


Input: The main result of the investigation is a demonstration of the technological feasibility to decrease the number and size of defects in complex LPBF-manufactured Alloy 800H constructions without changes in phase composition at high temperatures.

feasibility

defects

phase composition

Alloy

temperatures


Input: A multi-component and multi-phase-field modelling approach, combined with transformation kinetics modelling, was used to model microstructure evolution during laser metal powder directed energy deposition of Alloy 718 and subsequent heat treatments.

modelling

modelling

laser

model microstructure

evolution

powder

Alloy

directed energy deposition

heat treatments


Input: Experimental temperature measurements were utilised to predict microstructural evolution during successive addition of layers.

Experimental

microstructural evolution


Input: Segregation of alloying elements as well as formation of Laves and δ phase was specifically modelled.

Segregation

Laves

phase

alloying elements

as


Input: The predicted elemental concentrations were then used in transformation kinetics to estimate changes in Continuous Cooling Transformation (CCT) and Time Temperature Transformation (TTT) diagrams for Alloy 718.

predicted

Cooling

Temperature

Alloy


Input: Modelling results showed good agreement with experimentally observed phase evolution within the microstructure.

Modelling

phase evolution

microstructure


Input: The results indicate that the approach can be a valuable tool, both for improving process understanding and for process development including subsequent heat treatment.

be

tool

process

process

heat treatment


Input: Fused Filament Fabrication (FFF) is a widely used Additive Manufacturing (AM) technique.

Fused Filament Fabrication

FFF

Additive Manufacturing

AM


Input: Recently, mechanical properties of plastic FFF parts have been enhanced by adding short carbon fibers to the thermoplastic polymer filament to form a carbon fiber filled (CFF) polymer composite.

mechanical properties

plastic

short carbon fibers

thermoplastic polymer

filament

carbon fiber

polymer composite

FFF


Input: Unfortunately, improvements to the material properties of commercially available CFF filament are not well understood.

material properties

filament


Input: This paper presents a study of CFF FFF parts produced on desktop 3D printers using commercially available filament.

FFF

desktop 3D printers

filament


Input: Tensile test samples fabricated with CFF polymer composite and unfilled polymer were printed and then tested following ASTM D3039M.

Tensile test

samples fabricated

polymer composite

polymer


Input: The filament considered here was purchased from filament suppliers and included both CFF and unfilled PLA, ABS, PETG and Amphora.

filament

filament

PLA

ABS


Input: Results for tensile strength and tensile modulus show that CFF coupons in general yield higher tensile modulus at all print orientations and higher tensile strength at 0 ° print orientation.

tensile strength

tensile

tensile

tensile strength

print

print

orientations

orientation


Input: The addition of carbon fiber was shown to decrease tensile strength for some materials when printed with beads not aligned with the loading direction.

carbon fiber

tensile strength

materials

beads


Input: Additionally, CFF samples are evaluated for fiber length distribution (FLD) and fiber weight fraction, where it was found that the filament extrusion process contributes very little to fiber breakage.

samples

fiber length

distribution

fraction

fiber

filament

fiber

extrusion process


Input: Finally, fracture surfaces evaluated under SEM show that voids between the beads are reduced with CFF coupons, and poor interfacial bonding between fibers and polymer become a prominent failure mechanism.

fracture

voids

interfacial bonding

SEM

beads

fibers

polymer

failure mechanism


Input: Three-dimensional (3D) printing, or additive manufacturing, has been increasingly used in many fields, including the medicine, food, sensing, metal, automotive, and construction industries.

Three-dimensional

medicine

additive manufacturing

sensing

automotive

construction

metal


Input: Regardless of its growing applications, there are few of methods, guidelines, and specifications for measuring and quantifying the qualities of 3D printed objects.

specifications

3D printed


Input: In this study, for the first time, a non-contact, and non-destructive measurement method, a 3D structured light scanning system (3D-SLSS), was employed for evaluating the printing qualities of clay objects with different levels of visual defects (e.g., roughness and distortion).

measurement

scanning

defects

distortion

clay

roughness


Input: 3D scanned images of these clay samples were developed using 3D-SLSS.

images

clay


Input: Then, they were sliced along their sides (perpendicular to the base) to generate a number of two-dimensional (2D) plots, from which various parameters (e.g., sample total height [Htotal], outer diameter [DMouter], layer thickness [TL], layer width, [(WL], surface angle [Sα], semi-cross-sectional area [XA], and surface roughness [R]) were measured.

two-dimensional

parameters

sample

diameter

layer thickness

layer

surface angle

area

TL

surface roughness


Input: Compared with the designed object, the printed samples generally had reduced total height, diameter, and layer thickness; increased layer width; measurable distortion; and visible surface roughness.

designed

samples

diameter

distortion

layer thickness

layer

surface roughness


Input: Many of these were largely because the freshly printed clay deformed under the weight of the layers above.

clay

weight


Input: The distortion angle and area are two necessary parameters for quantifying the degree of distortion of a printed sample.

distortion

parameters

distortion

sample

area


Input: The diagnosed area of deficiency can well describe the overall qualities of the printed samples.

area

samples


Input: Moreover, it can be conveniently extended to various industries for quality control of diverse 3D printing products.

be

industries

quality control

3D printing


Input: TiB reinforced near α Ti-matrix composite was fabricated in this work using selective laser melting from a mixture of CrB2 and commercially pure Ti powders.

reinforced

fabricated

composite

Ti powders

selective laser melting


Input: The corresponding composites present an almost fully dense structure for suitable laser energy density conditions.

composites

fully dense

laser energy density


Input: The X-ray diffraction and microstructure analysis indicate that the TiB and β-Ti phase appears for parts obtained with a low scanning speed of the laser beam.

X-ray diffraction

microstructure

phase

laser beam

scanning speed


Input: The parts obtained at high and low scanning speeds show higher hardness and lower wear rate than those obtained for intermediate scanning speed which, on the contrary, show the highest density.

scanning speeds

scanning speed

hardness

density

wear


Input: The wear behavior of the as-processed parts is compared with that of pure Ti parts also obtained by selective laser melting.

wear

Ti

selective laser melting


Input: Fused Filament Fabrication (FFF) is a popular additive manufacturing technique where molten polymer filament is applied in a raster pattern, layer by layer, to obtain the work piece.

Fused Filament Fabrication

FFF

additive manufacturing

polymer filament

raster pattern

layer by layer

work piece


Input: A necessary consequence of this method is a pronounced mechanical anisotropy of the product; the interface between the filaments is weaker compared to the filament itself.

mechanical anisotropy

interface

filaments

filament


Input: The strength of this interface is governed by the reptation theory which postulates a more efficient interpenetration of polymeric surfaces with decreasing polymer viscosity.

strength

interface

surfaces

polymer


Input: This relationship was utilized in this work to modify a polycarbonate-acrylonitrile butadiene styrene polymer blend to produce FFF work pieces with less mechanical anisotropy, independent of printer settings.

polymer blend

FFF

mechanical anisotropy

printer


Input: The tensile strength ratio of the printed interface to bulk tensile strength could be increased from 41% to 95%.

tensile strength

tensile strength

interface

be


Input: Though the absolute bulk tensile strength decreases slightly, this method presents an easy and effective way to address the mechanical problems inherent in the FFF-method.

tensile strength

mechanical


Input: The systematic occurrence of porosities inside selective laser melted (SLM) parts is a well-known phenomenon.

porosities

selective laser melted

SLM


Input: In order to improve the density of SLM parts, it is important not only to assess the physical origin of the different types of porosities, but also to be able to measure as precisely as possible the porosity rate so that one may select the optimum manufacturing parameters.Considering 316 L steel parts built with different input energies, the current paper aims to (1) present the different types of porosities generated by SLM and their origins, (2) compare different methods for measuring parts density and (3) propose optimal procedures.

density

porosities

porosity

porosities

density

SLM

manufacturing

SLM

be

as

as

steel


Input: After a preliminary optimization step, three methods were used for quantifying porosity rate: the Archimedes method, the helium pycnometry and micrographic observations.The Archimedes method shows that results depend on the nature and temperature of the fluid, but also on the sample volume and its surface roughness.During the micrographic observations, it has been shown that the results depend on the magnification used and the number of micrographs considered.A comparison of the three methods showed that the optimized Archimedes method and the helium pycnometry technique gave similar results, whereas optimized micrographic observations systematically underestimated the porosity rate.In a second step, samples were analyzed to illustrate the physical phenomena involved in the generation of porosities.

optimization

sample

surface

magnification

step

samples

porosity

porosity

porosities

Archimedes method

Archimedes method

Archimedes method

helium

fluid

helium

temperature


Input: It was confirmed that: (1) low Volume Energy Density (VED) causes non-spherical porosities due to insufficient fusion, (2) in intermediary VED the small amount of remaining blowhole porosities come from gas occlusion in the melt-pool and (3) in excessive VED, cavities are formed due to the key-hole welding mode.

Volume

non-spherical

blowhole

gas

Energy Density

insufficient fusion

welding


Input: The eutectic Al-33Cu (wt.%) alloy was processed by selective laser melting.

eutectic

processed

alloy

selective laser melting


Input: Based on the interlamellar distances a local cooling rate can be calculated.

cooling rate

be


Input: At high laser powers the cooling rate is 104 K/s, at low laser powers it is 105 K/s.

laser powers

cooling rate

laser powers


Input: The thermal history of selectively laser-melted alloys can be explored.

alloys

be


Input: The cooling rates inherent to selective laser melting (SLM) were experimentally determined by processing the eutectic Al-33Cu (wt.%) alloy.

cooling rates

selective laser melting

SLM

eutectic

alloy


Input: Two different parameter sets yielding an identical volumetric energy density were employed to produce the samples.

parameter

samples

energy density


Input: Based on the average spacing of the Al and CuAl2 lamellae, the cooling rates in different parts of the SLM specimens were estimated.

average

Al

lamellae

cooling rates

SLM


Input: At a high laser power (300 W) the cooling rate amounts to 104 K/s and at the lower laser power (200 W) to 105 K/s.

laser power

cooling rate

laser power


Input: The present approach proves to be useful for exploring the thermal history of additively manufactured metallic components.

be

additively manufactured

components


Input: A 3D finite element simulation model of the laser cladding process has been developed taking into account heat transfer, fluid flow, surface tension and free surface movement.

model

heat transfer

free surface

element

laser cladding

fluid flow

surface tension


Input: All input parameters and data, which are independent of the process parameters but depend only on the material and machine properties, have been obtained from measurements.

parameters

data

process parameters

material

machine


Input: Thereby the melt pool and the resulting surface contour can be simulated without compromising assumptions or calibration, because the machine parameters are the only variable input parameters of the model.

melt pool

be

surface

calibration

parameters

model

contour

machine parameters


Input: Thus, the model can easily be transferred to other material combinations or other machines.

model

be

material

machines


Input: For the surface contour calculation a modified height function method is applied.

surface

contour


Input: The model surface follows this contour as an arbitrary Lagrangian Eulerian (ALE) method is used allowing for mesh deformations.

model

deformations

contour

as


Input: The model was implemented using the commercial finite element software COMSOL Multiphysics and validated by comparing the simulation results with caloric measurements of the effective heat input and metallographic cross sections from experiments, where the nickel-base alloy MetcoClad® 625 in powder form was deposited on structural steel S235JRC + C and the process parameters of laser power, feed speed, laser beam spot size and powder mass flow were varied within a range of at least 50% of their mean value each.

model

finite element

heat

cross sections

process parameters

laser beam

simulation

alloy

powder

steel

C

powder

laser power

feed

range


Input: The maximum deviation of the simulation results compared to the experimental data regarding track geometry is 14% for the parameter sets without weld defects so that these parameter sets could be industrially applied, whereas the average deviation of track width and height is below 5.1%.

simulation

experimental data

geometry

parameter

defects

parameter

average

weld

be


Input: A thermal analysis model of synchronous induction assisted laser deposition is established.

thermal analysis

model

deposition

laser


Input: The effect of the laser-induction interaction mode on the thermal behavior Microstructural evolution mechanisms of synchronous induction assisted laser deposition are revealed.

Microstructural evolution

deposition

laser


Input: The grains and phase can potentially be controlled separately by synchronous induction assisted laser deposition process.

grains

phase

be

laser

deposition process


Input: Synchronous induction-assisted laser deposition (SILD) can be used to address issues that arise from the extreme thermal behavior that occurs during direct energy deposition (DED).

laser

deposition

be

direct energy deposition

DED


Input: However, the incorporation of induction heating simultaneously renders the thermal behavior during SILD more flexible and complicated.

induction heating


Input: This study established a 3-D transient finite element model to elucidate the thermal behavior during SILD with a simplified inductive heat source.

finite element model

heat source


Input: It should also be noted that although it was more difficult to balance the thermal behavior, the cooling rate at the β transus temperature of Ti-6Al-4 V decreased from 82 ℃/s to 23 ℃/s; further, the maximum temperature gradient in front of the solid-liquid interface decreased from 5.8 × 105 ℃/m to 4.4 × 105 ℃/m in the “alternate” mode, which was relative to the “without induction heating” and “synchronous” modes.

be

Ti-6Al-4 V

cooling rate

temperature

temperature gradient

interface

induction heating


Input: Additive manufacturing (AM) is increasingly used for the production of functional parts.

Additive manufacturing

AM

production


Input: In order to ensure product reliability in challenging load cases and environments, a valid knowledge of the residual stress state is crucial.

product reliability

residual stress


Input: Since typical, complex AM geometries necessitate simulative efforts for this prediction, suitable validation data are essential.

AM

prediction

validation data


Input: This study presents results from neutron diffraction measurements on different stages of a build-up of a simple cuboid structure by laser beam melting.

neutron diffraction

simple

structure

laser beam


Input: The strain-free reference is obtained from measurements on small matchstick geometries cut from an analogously manufactured cuboid at the respective measurement spots.

geometries

manufactured

measurement


Input: By providing quasi-transient data of the evolution of residual stresses in both the base plate and the part, simulation models can be investigated towards their structural validity.

data

evolution

residual stresses

simulation

be


Input: Results indicate that the assumption of negligible shear strains may not be justifiable.

shear strains

be


Input: Additive manufacturing (AM) processes are being more frequently applied in several fields ranging from the industrial to the biomedical, in large part owing to their advantages which make them suitable for several applications such as scaffolds for tissue engineering, dental procedures, and 3D models to improve surgical planning.

Additive manufacturing

AM

planning

processes

tissue engineering

industrial

biomedical

dental

3D models

as


Input: Moreover, these processes are particularly suited for the fabrication of microfluidic devices and labs-on-a-chip (LOC) designed to work with biological samples and chemical reaction mixtures.An aspect not sufficiently investigated is related to the dimensional verification of these devices.

processes

samples

chemical reaction

verification

fabrication

designed


Input: The main criticality is the texture-less surface that characterizes the AM products and strongly affects the effectiveness of most currently available 3D optical measuring instruments.In this study, a passive photogrammetric scanning system has been used as a non-destructive and low-cost technique for the reconstruction and measurement of 3D printed microfluidic devices.

surface

effectiveness

scanning

reconstruction

AM

3D printed

as

measurement


Input: Four devices, manufactured with stereolithography (SLA), fused deposition modelling (FDM) a Stratasys trademark, also known as fused filament fabrication (FFF), and Polyjet have been reconstructed and measured, and the results have been compared to those obtained with optical profilometry that is considered as the gold standard.

manufactured

fused deposition

Polyjet

stereolithography

FDM

fabrication

FFF

SLA

Stratasys

as

filament

as

gold

optical


Input: Selective laser melting is a promising additive manufacturing technology for the production of complex metal components.

Selective laser melting

additive manufacturing

production

metal

components


Input: The technique uses metallic powder as a starting material and a laser for melting and building-up parts layer by layer.

metallic powder

as

material

laser

melting

layer by layer


Input: One crucial factor influencing the process stability and therefore the part quality is the shielding gas flow.

process

quality

gas


Input: In addition to the shielding properties of the inert atmosphere the gas flow is responsible for the removal of process by-products like spatter and welding fumes originating from the process zone.

properties

gas

process

process

spatter

welding


Input: Insufficient removal or inhomogeneous gas flow distribution may lead to increased interaction between laser and process by-products.

gas

distribution

process

lead

laser


Input: Consequences are attenuation of the laser spot as well as redeposition of this by-products on surfaces which are exposed to the laser afterwards.

laser

laser

as

as

surfaces


Input: Furthermore process deviations are provoked by unfavorable gas flow conditions.

process

gas


Input: Thirdly, the impact of this deviations on building surface and part quality is investigated by 3D confocal microscopy, microsections and ultrasonic testing.

impact

surface

quality

microscopy

testing


Input: Finally, theoretical approach for the formation of these process deviations and arising material defects is presented.

theoretical

process

defects

material


Input: The high-energy input and thermal history during additive manufacturing lead to complex phase transformations in titanium aluminide alloy.

additive manufacturing

phase

titanium aluminide alloy


Input: This study mostly focuses on determining the solid-state phase transformation mechanisms during laser deposition and the failure mechanisms of alloys using molecular dynamics simulations.

solid-state phase

deposition

laser

simulations

failure mechanisms

alloys


Input: Because of the directional temperature gradient, columnar grains with fully lamellar microstructures are formed first after solidification.

temperature gradient

columnar grains

lamellar

solidification


Input: A narrow region just below the melting pool is reheated to high temperatures, thus enhancing the precipitation of new equiaxed grains.

melting

temperatures

precipitation

equiaxed grains


Input: Multiple thermal cycles in the α + γ phase region promote the formation of massive γ phases (γm) at the grain boundaries.

thermal cycles

phase

grain boundaries


Input: Finally, a nearly lamellar microstructure of alternating columnar and equiaxed grains with γm phases is formed.

lamellar

equiaxed grains


Input: The deposited titanium aluminide alloy has good room and high-temperature (760 °C) tensile properties of 545 ± 9 and 471 ± 37 MPa, with elongations of 1.50% ± 0.47% and 1.50% ± 0.45%, respectively.

titanium aluminide alloy

tensile properties

MPa


Input: The room and high-temperature samples both fail in the columnar grain region.

samples

columnar grain


Input: Although the equiaxed grain regions contain several γm–α2 interfaces, the samples still fail in the columnar grain regions due to the increase in the cracking distance in the equiaxed regions caused by randomly oriented α2 + γ lamellae and the comparably good plasticity of the γm phases.

equiaxed grain

samples

cracking

columnar grain

plasticity

lamellae


Input: Multiple thermal cycles in the α + γ phase region promote the formation of a massive γ phase (γm) at the grain boundaries.

thermal cycles

phase

phase

grain boundaries


Input: Finally, a nearly lamellar microstructure of alternating arrangement of columnar and equiaxed grains with γm phases is formed.

lamellar

equiaxed grains


Input: Based on the relations among the orientations of the γm, γ, and α2 phases, five interface structure models can be established for the molecular dynamics simulations of TiAl alloy fabricated by directed energy deposition, which can be used to accurately predict the location of the crack nucleation sites during the tensile test.

orientations

interface

nucleation

be

alloy

be

simulations

directed energy deposition

accurately

tensile test


Input: Furthermore, we revealed, for the first time, that the interface between α2 and γm is the weakest, especially in the case of semicoherent interfaces (6° angle in the [1–10] direction), which provides good nucleation sites for cracks.Download: Download high-res image (322 Electron Beam Melting (EBM) is an increasingly used Additive Manufacturing (AM) technique employed by many industrial sectors, including the medical device and aerospace industries.

interface

nucleation

high-res image

industrial sectors

Electron Beam Melting

EBM

Additive Manufacturing

AM

medical device

aerospace industries


Input: In-situ EBM monitoring for quality assurance purposes has been a popular research area.

In-situ

quality

research

EBM

area


Input: Electronic imaging has recently been investigated as one of the in-situ EBM data collection methods, alongside thermal/optical imaging techniques.

imaging

imaging

as

in-situ

data

EBM

optical


Input: So far, the disseminations focus on the design of an electronic imaging system and the ability to generate electronic images in-situ, experiments are yet to be carried out to benchmark one of the most important features of any imaging systems–spatial resolution.

design

imaging

imaging

images

be

benchmark

resolution


Input: Analyses of experimental results indicated that the spatial resolution was of the order of 0.3 to 0.4 mm when electronic imaging was carried out at room temperature.

experimental

resolution

temperature

mm

imaging


Input: It is believed that by disseminating an analysis and experimental method to estimate and quantify spatial resolution, this study has contributed to the on-going quality assessment research in the field of in-situ monitoring of the EBM process.

experimental

quality

research

in-situ

resolution

EBM


Input: The thermal history developed in laser powder bed fusion (LPBF) processes has been shown to be complex resulting in equally complex microstructures and mechanical properties.

laser powder bed fusion

LPBF

processes

mechanical properties

be

microstructures


Input: Three-dimensional finite element analysis was used to simulate thermal history and to predict the residual stress distribution in the as-built material.

Three-dimensional

finite element analysis

distribution

residual stress

material


Input: Computational thermodynamics was used to predict the micro-segregation and nucleation driving force of various phases in the bulk and in segregated regions.

micro-segregation

nucleation

force


Input: Varied heat-treatments such as simulated hot isostatic pressing, and double aging were applied.

as

hot isostatic pressing


Input: Their influence on the microstructure, micro-segregation, precipitate formation, and micro-hardness variations of LPBF alloy 718 were investigated.

microstructure

micro-segregation

variations

precipitate

alloy

LPBF


Input: Hardness map results showed heterogeneous micro-hardness on the xy- and xz-planes of the as-built parts where the bottom plane and center regions had larger hardness of ∼315 HV0.5 while the top plane and contours showed hardness of ∼300 HV0.5.

Hardness

hardness

hardness

heterogeneous

contours


Input: After simulated hot isostatic pressing process (i.e., without applied pressure) at 1020 °C for 4 h followed by water quench (HIPWQ), the hardness gradient and hardness was minimized (∼210 HV0.5) as the microstructure transitioned from heterogeneous columnar grains in the as-built condition to more uniform recrystallized grains.

hot isostatic pressing

recrystallized

pressure

microstructure

heterogeneous

grains

hardness

hardness

columnar grains

as


Input: HIPWQ followed by double aging produced a homogeneous microstructure and more uniform hardness map with enhanced mechanical properties in LPBF alloy 718 coupons.

homogeneous

mechanical properties

hardness

LPBF

alloy


Input: Selective laser melting (SLM) is a promising manufacturing technique for the production of complex metallic components.

Selective laser melting

SLM

manufacturing

production

metallic

components


Input: One of the crucial factors influencing the mechanical properties of the final product is spatter particles formation during the process.

mechanical properties

particles

process

spatter


Input: In this study, high- speed photography is utilized to record the formation mechanisms and the dynamic behavior of spatter particles.

dynamic

particles

spatter


Input: An image processing analysis framework is utilized to assess the distribution of spatter particles under various energy inputs.

image

framework

distribution

particles

spatter


Input: It is found that changing the laser scan velocity has more influences on spatter formation in comparison with the energy input.

laser scan

spatter


Input: The relationship between the numbers of created spatter particles, induced unmelted regions and density variability are interpreted and discussed based on other observations, such as microscopic examination and density analysis of SLM parts.

spatter

particles

density

density

as

SLM


Input: The obtained results could be used to enhance the current manufacturing process parameters optimization methods in SLM process.

be

manufacturing process

SLM

optimization

process


Input: Principle of real-time feedback control is proven for ceramic vat photopolymerization.

feedback

ceramic

photopolymerization


Input: FTIR spectrometry equipment and UV LED are integrated into an embedded control system.

FTIR

equipment

control system

UV

LED


Input: Control-oriented process model shows good agreement to experimental data.

process model

experimental data


Input: Feedback controller successfully compensates for a material composition disturbance.

Feedback

controller

material

composition


Input: Technical ceramics for high-performance applications can be additively manufactured using vat photopolymerization technology.

ceramics

be

additively manufactured

vat photopolymerization

technology


Input: This technology faces two main challenges: increasing ceramic product size and improving product quality.

technology

product quality

ceramic


Input: The integration of process control strategies into AM equipment is expected to play a key role in tackling these challenges.

process control

AM


Input: This work demonstrates the feasibility of real-time and in-situ feedback control of the light-initiated polymerization reaction that lies at the core of vat photopolymerization technology.

feasibility

in-situ

technology

feedback

polymerization

vat photopolymerization

core


Input: Experimental data obtained from this setup was used to develop a control-oriented process model and identify its parameters.

Experimental data

process model

parameters


Input: The results show that the feedback controller successfully compensated for the material perturbation and reached the same final conversion value as the unperturbed case.

feedback

controller

material

as


Input: This result can be considered a fundamental step towards additive manufacturing of defect-free ceramic parts using in-line process control.

be

ceramic

step

process control

additive manufacturing


Input: Optimization of single track and single layer is required for high final quality.

Optimization

quality

layer


Input: Feedbacks between single track, single layer, and the 3D levels were established.

layer


Input: A multistep algorithm to find optimal SLM process parameters is described.

algorithm

process parameters

SLM


Input: The algorithm is illustrated for AISI 420 stainless steel as an example.

algorithm

AISI 420

steel

as


Input: Selective laser melting (SLM) is becoming a powerful additive manufacturing technology for different industries: automotive, medical, chemical, aerospace, etc.

Selective laser melting

SLM

additive manufacturing

industries

automotive

medical

aerospace


Input: SLM could dramatically narrow the time frames to optimize production, providing extraordinary freedom to validate design and to develop new materials.

SLM

production

design

materials


Input: The extension of applications requires different materials with specific properties and therefore tailored properties of the final product.

materials

properties

specific properties


Input: In this article, a hierarchical approach including mutual analysis of SLM parameters necessary to control the final product quality on every level–the track, the layer and the final 3D object–is suggested and discussed.

SLM

parameters

product quality

layer

3D object


Input: Numerical simulation allowed the estimation of temperature distribution during laser melting and predicted final microstructures and properties of a 3D SLM object.

Numerical simulation

laser

temperature

distribution

predicted

properties

microstructures


Input: A series of single tracks, layers and 3D objects were manufactured from AISI 420 stainless steel to validate a proposed algorithm.

3D objects

manufactured

algorithm

AISI 420

steel


Input: The efficiency of the approach was illustrated by the manufacturing of fully dense samples from AISI 420 stainless steel widely used in the plastics-moulding industry.

manufacturing

fully dense

AISI 420

steel

industry


Input: The results show that based on the proposed systematic hierarchical approach, optimal process parameters can be efficiently established for high-quality SLM parts from metal powders.

optimal process

be

metal powders

SLM


Input: High speed imaging with external illumination is used to analyse defects.

imaging

defects


Input: Power decay strategy to tackle heat accumulation in multiple layers is presented.

Power

heat accumulation


Input: Benchmark data of porosity, productivity, roughness, and microhardness is provided.

Benchmark

porosity

roughness

productivity

microhardness


Input: In this work, coaxial laser metal wire deposition (LMWD) process is studied, with particular attention to defect formation mechanisms and the establishment of stable processing conditions.

laser

deposition

process

defect


Input: The coaxial LMWD of AISI 308 stainless steel wire was carried out by a multi-mode fiber laser delivered to an industrial coaxial LMWD deposition head.

stainless steel

fiber

industrial

deposition


Input: The continuous mechanical connection with the deposition region requires further attention to the process dynamics, which may alter the deposition precision and continuity.

mechanical

deposition

process

deposition


Input: Accordingly, this work presents a systematic analysis of how the defects are formed at single and multiple layer deposition conditions.

defects

deposition

layer


Input: High-speed imaging is employed to reveal the process dynamics as a diagnostics aid.

imaging

process

as


Input: The process stability is determined initially at single layer condition, providing a correct match between the melting position and rate of the wire.

process

layer

melting


Input: At multiple layer deposition, the thermal load is managed to achieve high-aspect ratio components.

layer

deposition

components


Input: At the stable conditions, the process is benchmarked for porosity, surface roughness, and deposition rates.

process

porosity

surface roughness

deposition rates


Input: The use of additive manufacturing (AM) provides an opportunity to fabricate composite tooling molds in a rapidly and cost effectively manner.

additive manufacturing

AM

fabricate

composite

molds


Input: This work has shown the use of a polymer based infiltrated ceramics produced via binder jetting for producing composite tooling molds.

polymer

ceramics

composite

binder jetting

molds


Input: Here, molds based on silica sand as well as zircon sand have been printed on a S-Max 3D printer unit and subsequently impregnated with an epoxy system for yielding functional molds in the range of autoclave temperatures around 150–177 °C.

molds

3D printer

molds

autoclave

silica sand

as

as

sand

epoxy

range


Input: The mechanical properties of the infiltrated 3D printed materials have been investigated and it was observed that the polymer-infiltrated systems resulted in a compressive and flexural strength one order of magnitude higher than the non-infiltrated printed ceramic material.

mechanical properties

3D printed

flexural strength

magnitude

ceramic material


Input: A thermal analysis was also performed on both the infiltrated and non-infiltrated printed samples, and it was recorded that the incorporation of the polymer resulted in a larger coefficient of thermal expansion on the infiltrated systems.

thermal analysis

samples

polymer

coefficient of thermal expansion


Input: Here, a carbon fiber reinforced composite was manufactured with the infiltrated composite tooling molds printed in the S-Max unit, and it was observed that the assembled molds are capable of producing a successful composite material.

carbon fiber

composite

composite

composite material

manufactured

molds

molds


Input: The present work has demonstrated that a binder jetting process, is a feasible technology for producing thermostable low cost composite tooling molds.

binder jetting

technology

composite

molds


Input: In the present study, laser metal deposition (LMD) was used to produce compositionally graded refractory high-entropy alloys (HEAs) for screening purposes by in-situ alloying of elemental powder blends.

laser metal deposition

LMD

refractory

alloys

powder blends

in-situ

alloying


Input: A compositional gradient from Ti25Zr50Nb0Ta25 to Ti25Zr0Nb50Ta25 is obtained by incrementally substituting Zr powder with Nb powder.

Zr powder

Nb


Input: A suitable strategy was developed to process the powder blend despite several challenges such as the high melting points of the refractory elements and the large differences in melting points among them.

process

powder blend

as

elements

melting points

melting points

refractory


Input: The influence of the LMD process on the final chemical composition was analyzed in detail and the LMD process was optimized to obtain a well-defined compositional gradient.

LMD

LMD

chemical composition


Input: Microstructures, textures, chemical compositions and mechanical properties were characterized using SEM, EBSD, EDX, and microhardness testing, respectively.

Microstructures

chemical compositions

mechanical properties

microhardness

SEM

EBSD

EDX


Input: Compositions between Ti25Zr0Nb50Ta25 and Ti25Zr25Nb25Ta25 were found to be single-phase bcc solid solutions with a coarse grain microstructure.

be

bcc

grain


Input: Increasing the Zr to Nb ratio beyond the equiatomic composition results in finer and harder multiphase microstructures.

Zr

Nb

microstructures

composition


Input: The results shown in the present study clearly show for the first time that LMD is a suitable processing tool to screen HEAs over a range of chemical compositions.

LMD

tool

range

chemical compositions


Input: Open source 3-D printer to both fabricate slot die and functionalize.

source

fabricate

die


Input: Created a 3-D slot die printing system.

die


Input: Functional lab-grade slot dies may be 3-D printed.

dies

be


Input: Semiconductor films deposited with polymer slot die down to 17 nm.

Semiconductor

polymer

die


Input: Slot die coating is growing in popularity because it is a low operational cost and easily scaled processing technique for depositing thin and uniform films rapidly, while minimizing material waste.

die

coating

processing technique

material


Input: The complex inner geometry of conventional slot dies require expensive machining that limits accessibility and experimentation.

geometry

limits

dies

machining


Input: In order to overcome these issues this study follows an open hardware approach, which uses an open source 3-D printer to both fabricate the slot die and then to functionalize a 3-D slot die printing system.

source

fabricate

die

die


Input: Polymer materials are tested and selected for compatibility with common solvents and used to fabricate a custom slot die head.

Polymer materials

fabricate

die


Input: This slot die is then integrated into a 3-D printer augmented with a syringe pump to form an additive manufacturing platform for thin film semiconductor devices.

die

syringe

additive manufacturing

semiconductor


Input: The full design of the slot die system is disclosed here using an open source license including software and operational protocols.

design

die

source

software

protocols


Input: This study demonstrates that functional lab-grade slot dies may be 3-D printed using low-cost open source hardware methods A case study using NiO2 found an RMS value 0.486 nm, thickness of 17–49 nm, and a maximum optical transmission of 99.1%, which shows this additive manufacturing approach to slot die depositions as well of fabrication is capable of producing viable layers of advanced electronic materials.

dies

die

be

as

case study

materials

source

optical

additive manufacturing

fabrication


Input: Ball-milled Ti/TiC composite particles (TiC nanoparticles assembled on Ti microparticles) were designed, prepared, and mixed with Al-Si-Mg powder to fabricate an Al-Si-Mg-Ti alloy with TiC nanoparticles (Al-Si-Mg-Ti/TiC) by selective laser melting (SLM).

composite particles

Ti

powder

alloy

nanoparticles

nanoparticles

designed

fabricate

selective laser melting

SLM


Input: Microstructure features, solidification behavior, and mechanical properties were investigated, and the relationship among them was established.

Microstructure

solidification

mechanical properties


Input: The SLM-manufactured Al-Si-Mg-Ti/TiC material exhibited fine equiaxed-shaped α (Al) grains with nanoscale Si4Ti5 phases and Mg segregation along the grain boundaries.

material

Al

Mg

grains

grain boundaries


Input: This structure benefited from heterogeneous nucleation as well as the grain growth restriction capabilities of TiC nanoparticles on α (Al), fast diffusion of Ti in the superheated Al liquid, and high chemical activity of Ti to Si during solidification.

structure

heterogeneous nucleation

grain growth

nanoparticles

diffusion

solidification

as

as

Al

Ti

Al

Ti

Si


Input: Furthermore, Ti enrichment in some local areas of the high-temperature pool and the consequently intense Marangoni convection improved the wettability between TiC nanoparticles and liquid Al without the interfacial reaction.

Ti

Al

areas

wettability

nanoparticles


Input: Consequently, the SLM-manufactured Al-Si-Mg-Ti/TiC showed a high ultimate tensile strength of up to 562 ± 7 MPa and an elongation of up to 8.8% ± 1.3% before fracture.

ultimate tensile strength

elongation

MPa

fracture


Input: These increased mechanical properties are attributed to the combined effect of grain refinement and Orowan and load-bearing strengthening mechanisms.

mechanical properties

grain refinement

load-bearing


Input: In this work, the Direct Ink Writing (DIW) technique was used to produce three-dimensional Ti2AlC ceramic components with high, uniform porosity.

Ink

ceramic

DIW

three-dimensional

porosity


Input: Suitable formulations were developed, with appropriate rheological properties for extruding thin filaments through a nozzle with a diameter of 810 μm.

rheological properties

extruding

filaments

nozzle

diameter


Input: The main rheological properties of the inks were investigated to evaluate their behavior and flowability during the printing process.

rheological properties

printing process


Input: Porous Ti2AlC lattices were fabricated, in selected conditions, with uniform pore size and good interconnectivity, and sintered at 1400 °C in Ar.

Porous

lattices

fabricated

pore size

sintered

Ar


Input: Total porosity ranged from ∼44 to ∼63 vol%, and the mechanical strength ranged from ∼43 to 83 MPa.

porosity

mechanical strength

MPa


Input: The influence of the ink composition and heat-treatment conditions on the phase composition of the 3D porous structures was also evaluated.

ink

composition

phase composition


Input: The high thermal gradients experienced during manufacture via selective laser melting commonly result in cracking of high γ/γ′ Nickel based superalloys.

thermal gradients

manufacture

cracking

selective laser melting

Nickel based superalloys


Input: Such defects can not be tolerated in applications where component integrity is of paramount importance.

defects

be

component


Input: To overcome this, many industrial practitioners make use of hot isostatic pressing to ‘heal’ these defects.

industrial

hot isostatic pressing

defects


Input: The possibility of such defects re-opening during the component life necessitates optimisation of SLM processing parameters in order to produce the highest bulk density and integrity in the as-built state.In this paper, novel fractal scanning strategies based upon mathematical fill curves, namely the Hilbert and Peano-Gosper curve, are explored in which the use of short vector length scans, in the order of 100 μm, is used as a method of reducing residual stresses.

defects

parameters

integrity

scanning strategies

mathematical

component

SLM

density

residual stresses

as


Input: The effect on cracking observed in CM247LC superalloy samples was analysed using image processing, comparing the novel fractal scan strategies to more conventional ‘island’ scans.

cracking

samples

image


Input: Scanning electron microscopy and energy dispersive X-ray spectroscopy was utilised to determine the cracking mechanisms.Results show that cracking occurs via two mechanisms, solidification and liquation, with a strong dependence on the laser scan vectors.

Scanning electron microscopy

energy dispersive X-ray spectroscopy

cracking

cracking

solidification

laser scan


Input: Through the use of fractal scan strategies, bulk density can be increased by 2 ± 0.7% when compared to the ‘island’ scanning, demonstrating the potential of fractal scan strategies in the manufacture of typically ‘unweldable’ nickel superalloys.

density

be

nickel

scanning

manufacture


Input: Porous scaffolds were studied for weight bearing biomedical applications.

Porous scaffolds

weight

biomedical applications


Input: Compression samples were additively manufactured using electron beam melting.

Compression

additively manufactured

electron beam melting


Input: Reentrant and cubic Ti6Al4 V unit cell geometries were tested under compression.

V

unit cell

geometries

compression


Input: Cubic scaffold outperformed the reentrant scaffold at the same relative density.

scaffold

scaffold

relative density


Input: A cubic scaffold was proved suitable for load bearing biomedical applications.

scaffold

biomedical applications


Input: Ti6Al4V porous scaffolds of two unit cell geometries (reentrant and cubic) were investigated as candidates for load-bearing biomedical applications.

as

porous scaffolds

load-bearing

unit cell

geometries

biomedical applications


Input: Samples were fabricated using an Arcam A2 electron beam melting (EBM) machine and evaluated for geometric deviation from the original CAD design using a digital optical microscope.

Samples

fabricated

electron beam melting

EBM

machine

microscope

CAD

optical


Input: The mass and bounding volume of each sample were also measured to calculate the resulting relative density.

volume

sample

relative density


Input: The scaffolds were loaded in compression in the build direction to determine the relative modulus of elasticity and ultimate compressive load.

scaffolds

compression

modulus of elasticity

build direction


Input: Experimental results were used to calculate the Gibson and Ashby relation parameters for the studied unit cell geometries.

Experimental

parameters

unit cell

geometries


Input: The results suggest that samples with the cubic unit cell geometries, with struts oriented at an angle of 45° to the loading direction, exhibited higher stiffness than samples with the reentrant unit cell geometry at equivalent relative densities.

samples

unit cell

geometries

samples

unit cell

geometry

struts

stiffness

relative densities


Input: A cubic scaffold is verified to withstand high compressive loads (more than 71 kN) while having an approximate pore size in the range of 0.6 mm.

scaffold

pore size

range

mm


Input: The selective laser melting fabricated 304L stainless steel exhibited an excellent strength–ductility synergy.

selective laser melting

fabricated

stainless steel


Input: Massive stacking faults and annealing twins formed in the selective laser melting fabricated 304L stainless steel.

annealing

selective laser melting

fabricated

stainless steel


Input: The outstanding ductility is due to the activation of multiple deformation mechanisms.

ductility

deformation


Input: The microstructure, mechanical properties and deformation mechanisms of the 304L stainless steel (SS) additively manufactured by selective laser melting (SLM) were systematically investigated.

microstructure

mechanical properties

deformation

stainless steel

SS

additively manufactured

selective laser melting

SLM


Input: The SLM fabricated 304L SS contains two phases (face-centered-cubic γ-austenite and body-centered-cubic δ-ferrite) and exhibits a hierarchical microstructure with length scales spanning several orders of magnitude.

SLM

fabricated

microstructure

SS

length scales

magnitude


Input: The hierarchical microstructure includes the melt pools and slightly elongated columnar grains at the micron scale, cellular structures decorated with a high density of dislocations at the sub-micron scale and oxides at the nanoscale.

microstructure

dislocations

melt pools

oxides

columnar grains

density

micron

cellular structures

sub-micron


Input: Stacking faults formed due to the residual stress in addition to the low stacking fault energy of the 304L SS (19.2 mJ/m2) while massive annealing twins were generated arising from the combined effects of residual stress and intrinsic heat treatment.

residual stress

residual stress

SS

annealing

heat treatment


Input: The as built 304L SS exhibits a significantly enhanced strength–ductility synergy compared to that of wrought and annealed counterparts.

as

SS

wrought


Input: The enhanced yield strength stems from the hierarchically heterogeneous microstructure, while the outstanding tensile elongation is ascribed to the activation of multiple deformation mechanisms, involving the dislocation activities, the formation of stacking faults and mechanical twins, and the transformation-induced plasticity.

yield strength

tensile elongation

plasticity

heterogeneous

deformation

dislocation

mechanical


Input: Laser powder bed fusion (LPBF) additive manufacturing (AM) is developing with the goal of fabricating parts with high performance and high efficiency.

Laser powder bed fusion

LPBF

additive manufacturing

AM

fabricating

performance


Input: Laser power is the key factor to the efficiency, microstructure and performance in LPBF.

Laser power

microstructure

performance

LPBF


Input: In this work, the molten pool characteristics and spatter behavior in LPBF with a high power and a wide process window (from 350 W to 1550 W) are studied based on high-speed high-resolution imaging.

molten pool

process

spatter

LPBF

power

high-resolution


Input: The results show that the molten pool characteristics and spatter behavior depend on the laser input energy.

molten pool

spatter

laser


Input: The average ejection velocity and ejection angle increase with the laser power.

average

ejection

laser power


Input: The droplet column ejection and large spatters are prone to occur with a high-power laser.

droplet

ejection

high-power laser


Input: Furthermore, the times at which the vapor depression and the protrusion in the molten pool first occur decrease dramatically with an increase in the laser input energy.

molten pool

laser


Input: When the laser mode and spot size are kept constant, the laser power determines the amount of time required for melting, the vapor depression and the protrusion in LPBF to occur, while the laser scan velocity determines whether the laser dwell time is sufficient for these phenomena to form.

laser

laser scan

laser

spot size

laser power

dwell time

melting

LPBF


Input: Optimum distribution of relative density can enhance the bending stiffness of an architected cellular beam more than 120%.

distribution

relative density

bending

beam


Input: Optimally graded cellular beam samples are 3D printed using stereolithography.

beam

3D printed

stereolithography


Input: Experimental bending tests on 3D printed samples confirm the practicality of graded designs for developing advanced lightweight structures.

Experimental

bending tests

3D printed

designs

lightweight structures


Input: Periodic cellular materials can substantially improve the stiffness-to-weight ratio of structures.

cellular materials


Input: This improvement depends on the geometry of periodic cells.

geometry

cells


Input: This article presents the idea of enhancing the bending stiffness of an architected cellular beam by an optimum distribution of relative density through its length and/or across its thickness.

bending

beam

distribution

relative density


Input: Detailed finite element analysis (FEA) and experimental bending tests on specimens 3D printed by stereolithography validate the hybrid-homogenized modeling approach.

finite element analysis

experimental

bending tests

3D printed

stereolithography

modeling


Input: The hybrid-homogenized model facilitates transforming the general optimization problem into a shape optimization process with the relative density of unit cells as design variables.

model

optimization

optimization

unit cells

relative density

as


Input: The teaching-learning-based optimization (TLBO) algorithm is used to obtain the optimum relative density distribution, which maximizes the bending stiffness.

optimization

algorithm

distribution

relative density

bending


Input: The optimization results show a substantial increase in bending stiffness; as high as 43%, 155%, and 182% for a cellular beam graded through the length, across the thickness, and in both directions, respectively.

optimization

bending

as

as

beam


Input: It is found that varying the relative density of cells across the beam thickness is more effective than variation through the length.

relative density

cells

beam

variation


Input: Detailed FEA and experimental bending tests corroborate the optimization findings and confirm the practicality of such graded designs for developing advanced lightweight structures.

experimental

optimization

bending tests

designs

lightweight structures


Input: Investigating the effect of cell architecture also reveals that optimally graded cellular beams have a potential to outperform uniform cellular beams made out of ideal unit cells (Voigt bound for elastic properties) by reaching bending stiffness-to-density ratios greater than one.

cell

architecture

unit cells

elastic

bending


Input: The relatively simple graded cellular designs are beneficial in applications where high bending stiffness and low density are essential.

simple

bending

cellular designs

density


Input: Recent advances in additive manufacturing promise extending the presented grading strategy for polymeric, composite, and metallic 3D printed cellular materials to fabricate high performance lightweight structural elements at a relatively low cost.

additive manufacturing

3D printed

fabricate

composite

metallic

elements

materials

performance lightweight


Input: This study investigated the effect of trace lanthanum hexaboride (LaB6) addition on the microstructure and mechanical properties of an electron beam melting (EBM) processed Ti-6Al-4V component.

lanthanum

microstructure

mechanical properties

processed

electron beam melting

EBM

component


Input: LaB6 exhibited a significant effect on the grain structure, phase, and texture of the EBM-processed Ti-6Al-4V alloys.

grain structure

phase

texture

Ti-6Al-4V alloys


Input: Although prior-β columnar grains were observed in both Ti-6Al-4V and LaB6-modified Ti-6Al-4V (Ti-6Al-4V-LaB6), the width of the columnar grains decreased significantly with LaB6 addition.

columnar grains

columnar grains


Input: Alternating acicular α′ martensite and acicular α laths were distributed in the Ti-6Al-4V, whereas refined lamellar α + β structures were observed in the Ti-6Al-4V-LaB6.

martensite

lamellar


Input: We propose that the addition of LaB6 provided a large amount of heterogenous nucleation sites for solidification and α phase formation.

nucleation

solidification

phase


Input: Consequently, high tensile strength with considerable elongation was achieved in the EBM-processed Ti-6Al-4V modiﬁed by trace LaB6 addition.

tensile strength

elongation


Input: The purpose of this paper is to identify the key elements of a new hybrid process to produce high quality metal/plastic composites.

elements

composites

process

quality


Input: The process is a combination of Fused Deposition Modelling (FDM), vacuum forming and CNC machining.

process

Fused Deposition

FDM

forming

CNC machining


Input: The research aims to provide details of the proposed hybrid process, equipment used, and the experimental results of the composites produced.

research

process

experimental

equipment

composites


Input: The research has been separated into three study areas.

research

areas


Input: In the first, the hybrid process has been defined as a whole whereas the second area deals with the breakdown of steps to produce the metal/plastic composites.

process

as

composites

area


Input: The third area explains the varied materials used for the production and testing of the composites.

area

materials

production

testing

composites


Input: Composites have been made by joining copper (99.99% pure) mesh with ABS (acrylonitrile butadiene styrene).

Composites

copper

ABS

acrylonitrile butadiene styrene

joining


Input: Strain measurement has been carried out on Cu/ABS sample to analyse the effect of metal mesh and to verify the effectiveness of the hybrid process.

Strain

measurement

sample

effectiveness

process

metal


Input: The resulting composites (Cu/ABS) have also been subjected to tensile loading with different layers of metal mesh, followed by microstructural analysis and comparative studies to serve as a proof of the methodology.

composites

metal

as

tensile

microstructural analysis

methodology


Input: The results show that the proposed hybrid process is very effective in producing metal/plastic composites with lower strain values compared to the parent plastic indicating a lower level of deformation due to interlocking of the metal and plastic layers.

process

deformation

composites

plastic

metal

plastic

strain


Input: This effect has been reinforced by the tensile testing where the composites showed higher fracture load values compared to the parent plastic.

reinforced

fracture

tensile testing

composites

plastic


Input: Microstructural analysis shows the layer of metal mesh sandwiched between ABS layers indicating the existence of a bond holding the layers of metal and plastic together.

Microstructural analysis

layer

metal

ABS

metal

plastic


Input: These results demonstrate the capabilities and effectiveness of the proposed process that has shown promising results under tensile and static loading.

effectiveness

process

tensile


Input: High-mass-proportion TiCp/Ti6Al4V composites with fully dense prepared by directed energy deposition.

composites

fully dense

directed energy deposition


Input: The changes in microstructure and orientation relationship was discussed in detail.

microstructure

orientation


Input: Hardness, wear resistance, and thermal conductivity increased, while tensile performance decreased with increasing TiCp content.

Hardness

wear resistance

thermal conductivity

tensile

performance


Input: Titanium matrix composites (TMC) have potential applications in the aerospace industry because of their excellent performance.

Titanium

composites

aerospace industry

performance


Input: The comprehensive performance of TMC mainly depends on the matrix, reinforcement and interface characteristics.

performance

interface

reinforcement


Input: Crack-free high-mass-proportion TiCp/Ti6Al4Vcomposites were successfully prepared by directed energy deposition (DED).

directed energy deposition

DED


Input: Meanwhile, the refined α-Ti in the composites had a relatively weak texture.

composites

texture


Input: In addition, the interface between primary TiC and α-Ti was a semi-coherent interface, exhibiting a 112-0 α-Ti // [110] TiC, 1-100 α-Ti // 1-11 TiC orientation relationship, which facilitated the heterogeneous nucleation of Ti and improved bonding of primary TiC with the matrix.

interface

interface

orientation

heterogeneous nucleation

bonding

Ti


Input: With the increase in microhardness taking the form of a cubic function, the wear mechanism was found to transform from abrasive wear to slight delamination wear.

microhardness

wear mechanism

abrasive wear

delamination


Input: Due to the fact that both UMT and primary TiC bonded well with Ti64 matrix, they shared partial friction to protect matrix from severe abrasion, resulting in an excellent wear resistance of composites.

composites

friction

wear resistance


Input: Moreover, the thermal conductivity of 50% TiCp/Ti6Al4V was 9.063 W∙m-1∙K-1, which was nearly 26.5% higher than that of Ti6Al4V.

thermal conductivity


Input: Owing to the premature cracking of brittle UMT and dendritic TiC, the tensile strength and elongation of the composite with 50% TiCp were 515.5 MPa and 1.83%, which decreased by 45.8% and 78.8%, respectively.

cracking

MPa

brittle

tensile strength

elongation

composite


Input: Adding a high proportion of TiCp can significantly improve the hardness and wear resistance of TMC, whereas it is detrimental to the tensile performance of TMC.

hardness

wear resistance

tensile

performance


Input: The study have significant implications for the design of novel TMC, particularly for the aerospace industrial applications.

design

aerospace


Input: This paper presents the design of a high speed, high resolution silicon based thermal imaging instrument and its application to thermally image the temperature distributions of an electron beam melting additive manufacturing system.

design

high resolution

temperature

imaging

image

distributions

electron beam melting additive manufacturing system


Input: Typically, thermal images are produced at mid or long wavelengths of infrared radiation.

thermal images

infrared


Input: Using the shorter wavelengths that silicon focal plane arrays are sensitive to allows the use of standard windows in the optical path.

silicon

standard

optical


Input: It also affords fewer modifications to the machine and enables us to make use of mature silicon camera technology.

machine

camera

silicon


Input: With this new instrument, in situ thermal imaging of the entire build area has been made possible at high speed, allowing defect detection and melt pool tracking.

in situ

defect

imaging

build area

melt pool


Input: Melt pool tracking was used to implement an emissivity correction algorithm, which produced more accurate temperatures of the melted areas of the layer.

Melt pool

algorithm

melted

accurate

areas

layer


Input: Simple, one-step copper electrodeposition on conductive 3D objects Only the most conductive filament enables uniform electroplating.

Simple

electroplating

copper

filament

3D objects


Input: Electroplating with additives reduces the surface roughness of the print by 2.4x.

Electroplating

print

additives

surface roughness


Input: Electrical resistance improved by 100x after one-step electrodeposition Quality factor of 3D printed inductor is improved by 1740x after electrodeposition.

Electrical

Quality

3D printed


Input: 3D printing with electrically conductive filaments enables rapid prototyping and fabrication of electronics, but the performance of such devices can be limited by the fact that the most conductive thermoplastic-based filaments for 3D printing are 3750 times less conductive than copper.

3D printing

fabrication

3D printing

electrically

electronics

performance

filaments

be

filaments

copper

rapid prototyping


Input: This study explores the use of one-step electrodeposition of copper onto electrically conductive 3D printed objects as a way to improve their conductivity and performance.

copper

as

electrically

performance

3D printed

conductivity


Input: Comparison of three different commercially-available conductive filaments demonstrates that only the most conductive commercially available filament could enable one-step electrodeposition of uniform copper films.

filaments

filament

copper


Input: Electrodeposition improved the electrical conductivity and the ampacity of 3D printed traces by 94 and 17 times respectively, compared to the as-printed object.

electrical conductivity

3D printed


Input: The areal surface roughness of the objects was reduced from 9.3 to 6.9 μm after electrodeposition, and a further reduction in surface roughness to 3.9 μm could be achieved through the addition of organic additives to the electrodeposition bath.

surface roughness

surface roughness

reduction

be

additives


Input: Copper electrodeposition improved the quality factor of a 3D printed inductor by 1740 times and the gain of a 3D printed horn antenna by 1 dB.

Copper

quality

3D printed

3D printed

gain


Input: One-step electrodeposition is a fast and simple way to improve the conductivity and performance of 3D printed electronic components.

simple

3D printed

conductivity

performance

components


Input: The wide usage of Inconel 718 alloy is based on its fusion weldability and its availability in many different forms including cast, wrought and powder.

Inconel 718 alloy

powder

fusion

wrought

cast


Input: Thus with the emergence of additive manufacturing (AM) techniques for metals, Inconel 718 is a prime candidate for materials to be considered.

additive manufacturing

AM

metals

Inconel 718

be

materials


Input: Powders that have been developed for powder metallurgy are readily available for use in various AM processes such as selected laser melting (SLM) powder bed.

Powders

as

powder metallurgy

AM processes

SLM

laser

powder bed


Input: While much research has focused on optimizing the deposition parameters to achieve fully densified specimens, subsequent heat treatments and their effect on the microstructure also need to be understood.

research

deposition

microstructure

densified

heat treatments

be


Input: This study evaluated the microstructure of SLM specimens of Inconel 718 after various heat treatments and compared the resulting effect on the quasi-static mechanical properties.

microstructure

quasi-static

mechanical properties

SLM

heat treatments

Inconel 718


Input: Additive manufacturing (AM) has received a great deal of attention for the ability to produce three dimensional parts via laser heating.

Additive manufacturing

AM

heating

laser


Input: One recently proposed method of making microscale AM parts is through microscale selective laser sintering (μ-SLS) where nanoparticles replace the traditional powders used in standard SLS processes.

microscale

microscale

nanoparticles

standard

AM parts

laser sintering

SLS processes

powders


Input: However, there are many challenges to understanding the physics of the process at nanoscale as well as with conducting experiments at that scale; hence, modeling and computational simulations are vital to understand the sintering process physics.

physics

process

process physics

as

as

modeling

simulations

sintering


Input: At the sub-micron (μm) level, the interaction between nanoparticles under high power laser heating raises additional near-field thermal issues such as thermal diffusivity, effective absorptivity, and extinction coefficients compared to larger scales.

sub-micron

nanoparticles

power

laser

heating

as

diffusivity


Input: Thus, nanoparticle's distribution behavior and characteristic properties are very important to understanding the thermal analysis of nanoparticles in a μ-SLS process.

distribution

properties

nanoparticles

process

thermal analysis


Input: This paper presents a discrete element modeling (DEM) study of how copper nanoparticles of given particle size distribution pack together in a μ-SLS powder bed.

element

copper

particle size distribution

powder bed


Input: Initially, nanoparticles are distributed randomly into the bed domain with a random initial velocity vector and set boundary conditions.

nanoparticles

boundary conditions

bed

set


Input: The particles are then allowed to move in discrete time steps until they reach a final steady state position, which creates the particle packing within the powder bed.

particles

steady state

particle

powder bed


Input: The particles are subject to both gravitational and cohesive forces since cohesive forces become important at the nanoscale.

particles

forces

forces


Input: A set of simulations was performed for different cases under both Gaussian and log-normal particle size distributions with different standard deviations.

set

simulations

Gaussian

particle size distributions

standard deviations


Input: In addition, this paper suggests a potential method to overcome the agglomeration effects in μ-SLS powder beds through the use of colloidal nanoparticle solutions that minimize the cohesive interactions between individual nanoparticles.

powder beds

colloidal

nanoparticles


Input: Grain morphology control is a challenging issue for additive manufactured NiTi alloy, which directly affects the functional properties.

Grain

properties

additive manufactured

alloy


Input: In this work, La2O3 addition was applied to control microstructure and improve functional properties of directed energy deposited (DED) NiTi alloy.

NiTi alloy

microstructure

properties

DED


Input: The results showed that the DEDed NiTi alloy mainly consisted of NiTi (B2) columnar grains and some coarse NiTi2 phases within and at the boundaries of NiTi grains.

NiTi alloy

NiTi

NiTi

columnar grains

boundaries

grains


Input: The addition of La2O3 led to the promotion of columnar-to-equiaxed transition and grain refinement of NiTi (B2) phase.

NiTi

transition

phase

grain refinement


Input: La2O3 and LaNi secondary phases can be found in the DEDed NiTi alloy with La2O3 addition.

be

NiTi alloy


Input: The La2O3 precipitate could act as the effective heterogeneous nucleation site and the NiTi2 or LaNi precipitates could pin the grain boundaries contributing to the grain refinement and the formation of equiaxed grains of NiTi (B2) phase.

as

precipitates

NiTi

heterogeneous nucleation

grain boundaries

equiaxed grains

phase

grain refinement


Input: The introduction of La2O3 could also refine the phase size and adjust morphology of NiTi2 phase, which was attributed to the increase of nucleation sites and more dispersed L (Ti-rich) .The temperatures and latent heat of phase transformation evidently increase with La2O3 addition due to the decrease in the Ni content and La dissolved into NiTi (B2) phase.

Ni

La

NiTi

phase

morphology

phase

nucleation

heat

phase

phase

temperatures


Input: Improved superelasticity property was achieved after La2O3 addition owing to the promotion of grain order and yield strength of NiTi (B2) phase and the reduction of resistance from NiTi2 phase for the interface movement.

property

grain

phase

reduction

phase

interface

NiTi

yield strength

resistance


Input: Mechanisms underlying the evolution of texture and microstructure during selective laser melting (SLM) and their combined effects on the mechanical response of 316L stainless steel are presented.

evolution

microstructure

mechanical response

texture

selective laser melting

SLM

316L stainless steel


Input: Long columnar grains with a fiber texture < 110 > || build direction (BD) evolved in the SLM printed material.

columnar grains

fiber

material

build direction

SLM


Input: Fiber texture was stronger in the horizontal build compared to the vertical build.

Fiber

build

build

vertical


Input: Use of bidirectional scanning strategy enforced epitaxial growth of grains across melt pools present within a single printed layer.

scanning strategy

grains

epitaxial

melt pools

layer


Input: < 110 > || BD texture evolved as a consequence of maintaining the balance between epitaxy and growth of [100] along maximum thermal gradient.

texture

as

epitaxy

thermal gradient


Input: High dislocation density and not grain size effect of the ultra-fine cellular structure, imparted high strength to 316L.

dislocation density

grain size

strength

cellular structure


Input: Lower average Schmid factor and smaller effective grain size in the horizontal build by virtues of crystallographic and morphological textures, respectively, imparted higher yield strength than the vertical build.

average

vertical

grain size

yield strength

build

build


Input: The horizontal build demonstrated higher strain hardening rate in the early stages of deformation compared to the vertical build due to higher crystallographic texture dependent twinning.

build

build

strain hardening

deformation

vertical

twinning

texture


Input: However, the higher rate of dislocation annihilation led to a continuous decline in the strain hardening rate of the horizontal build.

dislocation

led

strain hardening

build


Input: In contrast, a stable strain hardening rate was maintained in the vertical build, which led to higher ductility than the horizontal build.

strain hardening

vertical

build

build

led

ductility


Input: In summary, the roles of non-equilibrium microstructure and texture (crystallographic and morphological) in regulating mechanical properties elucidated here, can be utilized in designing additively manufactured structural components of 316L stainless steel.

microstructure

mechanical properties

texture

be

316L stainless steel

additively manufactured

components


Input: Spatter particles ejected from the melt pool after melting of 316 L stainless steel by laser powder bed fusion additive manufacturing (LPBF), were found to contain morphologies not observed in as-atomized 316 L powder.

Spatter

particles

morphologies

melt pool

stainless steel

powder

melting

laser powder bed fusion additive manufacturing

LPBF


Input: This spatter consisted of large, spherical particles, highly dendritic surfaces, particles with caps of accreted liquid, and agglomerations of multiple individual particles fixed together by liquid ligaments.

spatter

spherical particles

surfaces

particles

particles


Input: The focus of this study is on an additional, unique spatter morphology consisting of larger, spherical particles with surface oxide spots exhibiting a wide distribution of surface configurations, including organized patterning.

spatter

morphology

spherical particles

surface

distribution

surface

oxide


Input: Spatter particles with organized surface oxide patterns were characterized for surface and internal particle features using multiple imaging techniques.

Spatter

particles

surface

surface

particle

oxide

imaging


Input: The following observations are made: 1) spots resided at the spatter particle surface and did not significantly penetrate the interior, 2) the spot (s) were amorphous and rich in Silicon (Si) -Manganese (Mn) -Oxygen (O), 3) a two-part Chromium (Cr) -O rich layer exists between the particle and spot, 4) Cr-O rich morphological features were present at the top surface of the spots, 5) the spatter particle composition was consistent with 316 L but appeared to decrease in Si content into the spatter particle away from a spot, and 6) small Si-rich spherical particles existed within the spatter particle interior.

spatter

spatter

spatter

spatter

particle

particle

surface

particle

composition

particle

spherical particles

particle

s

Silicon

Si

Mn

O

Chromium

Cr

Si

layer


Input: In this study, the fatigue properties of binder-jet 3D-printed nickel-base superalloy 625 were evaluated.

fatigue


Input: Standard fatigue specimens were printed and sintered, then half of the samples were mechanically ground, while the other half were left in their as-sintered state.

Standard

samples

fatigue

sintered

as-sintered


Input: They were then characterized using micro-computed x-ray tomography, metallographic sample examination, and optical and stylus profilometry for surface topography.

x-ray tomography

optical

sample

surface topography

stylus


Input: The micro-computed tomography observations showed that density of the as-printed sample was ∼50%, while the sintered sample neared full densification (98.9 ± 0.3%) upon sintering at 1285 °C for 4 h in a vacuum atmosphere.

micro-computed tomography

density

sample

sample

sintered

densification

sintering


Input: The metallographic examination showed equiaxed grains.

equiaxed grains


Input: The roughness of the as-sintered samples was significant with an RMS roughness of Rq = 1.39 ± 0.20 μm as measured over a line-scan of 5 mm, but this was reduced to Rq = 0.47 ± 0.02 μm after mechanical grinding.

roughness

roughness

as-sintered

mm

grinding

as

mechanical


Input: All samples were tested to failure in fatigue, under fully-reversed tension-compression conditions.

samples

failure

fatigue


Input: While the as-sintered samples showed poor fatigue properties compared to prior reports on cast and milled parts, the ground samples showed superior performance.

as-sintered

cast

milled

fatigue

samples

performance


Input: Scanning electron microscopy observation was conducted on the fractured surfaces and showed that the samples underwent transgranular crack initiation, followed by intergranular crack growth and final failure.

Scanning electron microscopy

surfaces

samples

crack growth

failure


Input: In the mechanically ground sample, hardness increased nearly two-fold up to 75 μm beneath the sample’ s surface, and X-ray diffraction indicated an in-plane compressive stress, grain refinement, and micro-strain on the mechanically ground sample.

sample

sample

sample

hardness

compressive stress

s

X-ray diffraction

grain refinement


Input: The reduced roughness, surface hardening, and compressive stress resulted in increased fatigue life of the binder-jetted alloy 625.

roughness

compressive stress

fatigue life

surface hardening

alloy


Input: Every SLM-fabricated component typically possesses a process-specific microstructure that fundamentally differs from any conventionally fabricated specimen.

component

microstructure

fabricated


Input: This publication addresses the evaluation of microstructure-related influencing factors on the resistance against cavitation erosion.

resistance

cavitation


Input: We exemplarily compared the findings to a cast and hot rolled reference sample.

cast

sample


Input: Due to careful adjustment of the process parameters, the overall cavitation erosion resistance of both SLM-processed and conventionally fabricated 316L are very much alike in the investigated case.

process parameters

cavitation

fabricated

resistance


Input: The incubation period of intact surface areas is improved by the greater hardness and yield strength of the SLM specimen, which is attributable to an increased dislocation density and a smaller grain size.

surface areas

hardness

yield strength

dislocation density

grain size

SLM


Input: Nevertheless, processing and powder feeding during SLM-fabrication occasionally results in microstructural defects, at which pronounced mass loss during cavitation was registered.

powder feeding

microstructural defects

cavitation


Input: X-ray measurements of the residual stresses reveal the development of severe compressive stresses that emerge after a few seconds of cavitation.

X-ray

residual stresses

compressive stresses

cavitation


Input: This compressive stress state delays the immediate propagation of SLM-inherent micro cracks.

compressive stress


Input: Moreover, investigations of the microstructure in combination with examination of the ongoing surface deformation highlighted the emergence of coarse grains that grew towards the temperature gradient.

microstructure

surface

deformation

grains

temperature gradient


Input: This effect leads to a temporarily high surface roughness, local stress concentrations and an increased probability of cavitation impacts.

surface roughness

local stress concentrations

probability

cavitation


Input: Selective laser melting (SLM) wherein a metal part is built in a layer-by-layer manner in a powder bed is a promising and versatile way for manufacturing components with complex geometry.

Selective laser melting

SLM

manufacturing

metal

layer-by-layer

complex geometry

powder bed

components


Input: However, components built by SLM suffer from substantial deformation of the part and residual stresses.

components

SLM

deformation

residual stresses


Input: Residual stresses arise due to temperature gradients inherent to the process and the accompanying deformation.

Residual stresses

temperature gradients

process

deformation


Input: It is well known that the SLM process parameters and the laser scanning strategy have a substantial effect on the temperature transients of the part and henceforth on the degree of deformations and residual stresses.

SLM

process parameters

deformations

laser

temperature

residual stresses


Input: In order to provide a tool to investigate this relation, a semi-analytical thermal model of the SLM process is presented which determines the temperature evolution in a 3D part by way of representing the moving laser spot with a finite number of point heat sources.

tool

model

process

evolution

heat sources

SLM

temperature

3D part

laser


Input: The solution of the thermal problem is constructed from the superposition of analytical solutions for point sources which are known in semi-infinite space and complimentary numerical/analytical fields to impose the boundary conditions.

solution

analytical solutions

boundary conditions


Input: The unique property of the formulation is that numerical discretisation of the problem domain is decoupled from the steep gradients in the temperature field associated with localised laser heat input.

property

domain

temperature

laser heat


Input: This enables accurate and numerically tractable simulation of the process.

accurate

simulation

process


Input: The predictions of this semi-analytical model are validated by experiments and the exact solution known for a simple thermal problem.

predictions

model

solution

simple


Input: Simulations for building a complete layer using two different scanning patterns and subsequently building of multiple layers with constant and rotating scanning patterns in successive layers are performed.

Simulations

layer

scanning patterns

scanning patterns


Input: The computational efficiency of the semi-analytical tool is assessed which demonstrates its potential to gain physical insight in the full SLM process with acceptable computational costs.

computational efficiency

process

tool

gain

SLM


Input: This work investigated the processing of high nitrogen-alloyed austenitic stainless steels by laser powder bed fusion (L-PBF).

austenitic stainless steels

laser powder bed fusion

L-PBF


Input: Prior to L-PBF processing, the AISI 316 L steel powder was nitrided at a temperature of 675°C in a 3 bar nitrogen atmosphere, thus achieving a N content of 0.58 mass-%.

L-PBF

nitrided

steel powder

nitrogen

N

temperature


Input: By mixing nitrided 316 L powder with untreated 316 L powder, two different powder mixtures were obtained with 0.065 mass-% and 0.27 mass-% nitrogen, respectively.

mixing

powder

powder

powder

nitrogen


Input: After nitriding and mixing, the powder was characterized in terms of its flow properties and chemical composition.

nitriding

mixing

properties

chemical composition

powder


Input: The nitrided steel powder was then processed by L-PBF, and the microstructure as well as the chemical composition were investigated by means of scanning electron microscopy and carrier gas hot extraction.

nitrided

L-PBF

powder

as

as

processed

microstructure

chemical composition

gas

scanning electron microscopy


Input: It was shown that nitriding of steel powders in an N2 atmosphere can be used to significantly increase the nitrogen content of the powder without impairing its flow properties.

nitriding

steel powders

be

nitrogen

powder

properties


Input: With increasing nitrogen content of the powder, the porosity within the L-PBF built specimens increased.

nitrogen

powder

porosity

L-PBF


Input: However, both the yield strength and the tensile strength were greatly improved without a marked reduction in the elongation at fracture of the respective steels.

yield strength

tensile strength

elongation

reduction

fracture

steels


Input: This work shows that nitrogen-alloyed austenitic stainless steels can be processed by L-PBF and the mechanical properties can be improved.

austenitic stainless steels

be

be

L-PBF

mechanical properties


Input: Laser powder bed fusion (LPBF) has broad application prospects due to its high fabrication accuracy and excellent performance, but the dynamic mechanical properties of LPBF components are relatively low due to defects of the melt track such as protrusions and depressions, whose generation mechanisms remain unclear.

Laser powder bed fusion

LPBF

fabrication

LPBF

accuracy

performance

dynamic

properties

defects

melt

components

as


Input: In this work, we investigate the correlation between the ex situ melt track properties and the in situ high-speed, high-resolution characterization.

melt

properties

in situ

high-resolution


Input: We correlate the protrusion at the starting position of the melt track with the droplet ejection behaviour and backward surging melt.

melt

droplet

melt


Input: We also reveal that the inclination angles of the depression walls are consistent with the ejection angles of the backward-ejected spatter.

inclination angles

ejection

spatter


Input: Furthermore, we quantify the vapour recoil pressure by in situ characterization of the deflection of the typical forward-ejected spatter.

pressure

in situ

spatter


Input: Our results clarify the intrinsic correlation of the melt track properties, which is important for the stable LPBF formation with few defects.

melt

properties

defects

LPBF


Input: Fused filament fabrication (FFF) 3D printers have been largely limited to thermoplastics in the past but with new composite materials available on the market there are new possibilities for what these machines can produce.

Fused filament fabrication

FFF

3D printers

machines

thermoplastics

composite materials


Input: Using a conductive composite filament, electronic components can be manufactured but due to the filament’ s relatively poor electrical properties, the resulting traces are typically highly resistive.

composite

be

filament

s

components

electrical properties


Input: Selective electroplating on these parts is one approach to incorporate materials with high conductivity onto 3D-printed structures.

electroplating

materials

conductivity


Input: In this paper, non-conductive and conductive filaments printed in the same part are used to enable selective electroplating directly on regions defined by the conductive filament to create metallic parts through 3D printing.

filaments

filament

electroplating

3D printing

metallic parts