To clarify the densification behavior,deformation response and strengthening mechanisms of selective laser melted(SLM)Mg-RE alloys,this study systematically investigates a representative WE43 alloy via advanced materi...To clarify the densification behavior,deformation response and strengthening mechanisms of selective laser melted(SLM)Mg-RE alloys,this study systematically investigates a representative WE43 alloy via advanced material characterization techniques.A suitable laser output mode fell into the transition mode,allowing for the fabrication of nearly full-density samples(porosity=0.85±0.021%)with favorable mechanical properties(yield strength=351 MPa,ultimate tensile strength=417 MPa,the elongation at break=6.5%and microhardness=137.9±6.15 HV_(0.1))using optimal processing parameters(P=80 W,v=250 mm/s and d=50μm).Viscoplastic self-consistent analysis and transmission electron microscopy observations reveal that the plastic deformation response of the SLM Mg-RE alloys is primarily driven by basal and prismatic slips.Starting from a random texture before deformation(maximum multiple of ultimate density,Max.MUD=3.95),plastic stretching led the grains to align with the Z-axis,finally resulting in a{0001}<1010>texture orientation after fracture(Max.MUD=8.755).Main phases of the SLM state are mainly composed ofα-Mg,Mg_(24)Y_(5) andβ'-Mg_(41)Nd_(5),with an average grain size of only 4.27μm(about a quarter of that in the extruded state),resulting in a favorable strength-toughness ratio.Except for the nano-β'phase and semi-coherent Mg_(24)Y_(5) phase(mismatch=16.12%)around the grain boundaries,a small amount of nano-ZrO_(2) and Y_(2)O_(3) particles also play a role in dispersion strengthening.The high mechanical properties of the SLM state are chiefly attributed to precipitation hardening(44.41%),solid solution strengthening(34.06%)and grain boundary strengthening(21.53%),with precipitation hardening being predominantly driven by dislocation strengthening(67.77%).High-performance SLM Mg-RE alloy components were manufactured and showcased at TCT Asia 2024,receiving favorable attention.This work underscores the significant application potential of SLM Mg-RE alloys and establishes a strong foundation for advancing their use in the biomedical fields.展开更多
The effects of various heat treatments on the microstructures and mechanical properties of as-built selective laser melted Inconel 718 alloy were investigated through conventional and quasi-in-situ tensile tests.The c...The effects of various heat treatments on the microstructures and mechanical properties of as-built selective laser melted Inconel 718 alloy were investigated through conventional and quasi-in-situ tensile tests.The corresponding heat treatment processes include direct aging(DA),solution+aging(SA),and homogenization+aging(HA).The DA and SA samples preserve the melt pool configuration and grain size stability,while the precipitated phase characteristics reveal the refinement of the long-strip Laves phase and the appearance of theδphase,respectively.The HA process induces recrystallization and grain coarsening.The specimens exhibit enhanced strength concomitant with diminished elongation,which is likely attributed to the reduction of the geometrically necessary dislocation density and the intensified precipitation of theγ′′phase after heat treatment.Tensile plastic deformation displays notable strain concentration along grain boundaries.The dimensional alterations in precipitated phases were measured to quantitatively determine the impact of grain boundary,dislocation and precipitation strengthening on the yield strength after heat treatment.Precipitation strengthening encompasses coherent,order,and Orowan strengthening.A remarkable agreement is revealed between theoretical predictions and experimental results.Insights are offered for optimizing heat treatment processes to comprehend microstructural evolution effect on the mechanical properties of additive-manufactured metals.展开更多
A gradient nanostructured layer was fabricated on the surface of TA15(Ti-6Al-2Zr-1Mo-1V)alloy(produced by selective laser melting)using severe shot peening(SSP).This study focuses on the evolution of the microstructur...A gradient nanostructured layer was fabricated on the surface of TA15(Ti-6Al-2Zr-1Mo-1V)alloy(produced by selective laser melting)using severe shot peening(SSP).This study focuses on the evolution of the microstructure and the mechanism of grain refinement in TA15 titanium alloy during SSP treatment.Transmission electron microscopyand Rietveld refinement methods were employed.The residual stress and microhardness variations with depth were also characterized.The results show:(1)At the initial stage of deformation,plastic deformation is primarily accommodated through twinning and dislocation slip.(2)As the strain increases,twinning disappears,and dislocations interact to form tangles.Some dislocations annihilate and rearrange into subgrain boundaries,subdividing the original grains into subgrains.(3)With continued dislocation activity,the subgrain size decreases until nanocrystals are formed through the dynamic rotational recrystallization.SSP introduced compressive residual stress(CRS)in the near-surface layer of the material,with the maximum CRS of approximately−1141 MPa observed in the subsurface layer.It also induced work hardening,increasing the surface hardness to approximately 479 HV.However,the surface roughness increases,leading to a slight deterioration in surface quality.展开更多
In the original publication,mistakenly first and corresponding affiliation is given as:Thermoelectricity Technology Center,Hangzhou Dahe Thermo-Magnetics Co.Ltd,Hangzhou 310053,ChinaThe correct first and corresponding...In the original publication,mistakenly first and corresponding affiliation is given as:Thermoelectricity Technology Center,Hangzhou Dahe Thermo-Magnetics Co.Ltd,Hangzhou 310053,ChinaThe correct first and corresponding affiliation is:State Key Laboratory of Silicon Materials,School of Materials Science and Engineering,Zhejiang University,Hangzhou 310027,China.展开更多
Selective laser melting(SLM)has become a critical technique for manufacturing molds with conformal cooling channels to achieve high cooling efficiencies.A novel selective laser-melted 718HH plastic mold steel with an ...Selective laser melting(SLM)has become a critical technique for manufacturing molds with conformal cooling channels to achieve high cooling efficiencies.A novel selective laser-melted 718HH plastic mold steel with an excellent combination of strength and toughness was investigated.After SLM fabrication,quenching and tempering are conducted as post-printing heat treatment(PPHT)to improve the mechanical properties of the as-built samples.Both the microstructure and the corresponding mechanical properties were systematically studied.The results show that PPHT facilitates the complete martensite transformation.Meanwhile,the retained austenite(γ)phase was still found in the as-built samples.And high-density dislocations were dispersively distributed within the martensite matrix for both as-built and as-PPHTed samples.After PPHT,due to the recovery and recrystallization of martensite,reduced dislocation density and increased high-angle grain boundaries,the microhardness of the as-built samples decreased from 498.8±16.7 to 382.1±5.0 HV0.3.Correspondingly,the strength,including the ultimate tensile strength and yield strength,of the as-built and as-PPHTed samples also decreased from 1411.3±17.8 to 1208.7±3.2 MPa and 1267.3±11.7 to 1084.7±5.1 MPa,respectively.On the contrary,the value of impact energy significantly increased from 15.3±1.2 J(as-built)to 39.7±1.2 J(as-PPHTed).Notably,the mechanical properties of SLMed 718HH samples are significantly better than those of corresponding wrought samples.展开更多
Only a few studies have reported the efects of electrochemical hydrogenation on the tensile mechanical properties of additively manufactured Ti–6Al–4V alloy,in all of them the alloy was processed by laser powder-bed...Only a few studies have reported the efects of electrochemical hydrogenation on the tensile mechanical properties of additively manufactured Ti–6Al–4V alloy,in all of them the alloy was processed by laser powder-bed fusion.Furthermore,the efects of either hot isostatic pressing(HIP)or heat treatment(HT)post-treatments on the mechanical properties were not reported.Here,the Young’s modulus,ultimate tensile stress,and uniform(homogeneous)strain of as-built electron beam melted(EBM)Ti–6Al–4V alloys were studied using small tensile specimens before and after electrochemical hydrogenation,as well as before and after secondary processes of HIP at 920℃ and HT at 1000℃.The tensile properties of all hydrogenated alloys were signifcantly degraded compared to their non-hydrogenated counterparts.The yield stress could not be determined for all hydrogenated alloys,as failure occurred at a strain below 0.2%ofset.The uniform strain of the hydrogenated alloys was less than 1%,compared to 1%–5%for the non-hydrogenated alloys.The fracture mode of the hydrogenated alloys after HIP and HT revealed cleavage fracture,indicating increased brittleness.In the as-built hydrogenated alloy,the fracture mode varied with location:brittle fracture occurred near the surface due to the formation of a hydride layer,while a more ductile fracture with dimples was observed below this layer.展开更多
To improve the processability and mechanical properties of the selective laser melting(SLM)low Sc content Al−Mg−Sc−Zr alloy,Mn was used to partially replace Mg.The processability,microstructure,and mechanical properti...To improve the processability and mechanical properties of the selective laser melting(SLM)low Sc content Al−Mg−Sc−Zr alloy,Mn was used to partially replace Mg.The processability,microstructure,and mechanical properties of the SLM-fabricated Al−Mg−Mn−Sc−Zr alloy were systematically investigated by density measurement,microstructure characterization,and tensile testing.The results revealed that dense samples could be obtained by adjusting the SLM process parameters.The alloy exhibited a fine equiaxed-columnar bimodal grain microstructure.The presence of primary Al3Sc andα-Al(Mn,Fe)Si particles contributed to the grain refinement of the alloy with an average grain size of 4.63μm.Upon aging treatment at 350°C for 2 h,the strength and elongation of the alloy were simultaneously improved due to the precipitation of Al3Sc nanoparticles and the formation of the 9R phase.This study demonstrates that the strength−plasticity trade-off of the aluminum alloy can be overcome by utilizing SLM technology and subsequent post-heat treatment to induce the formation of the long-period stacked ordered phase.展开更多
Cellular microstructure is a unique feature in alloys fabricated by selective laser melting(SLM).Abundant efforts have been made to reveal the formation mechanism of cellular microstructures and its influences on mech...Cellular microstructure is a unique feature in alloys fabricated by selective laser melting(SLM).Abundant efforts have been made to reveal the formation mechanism of cellular microstructures and its influences on mechanical performances,while its potential role in microstructure architecting during post-heat treatment is rarely explored.In this work,we investigated the features of cellular microstructures in an SLM-fabricated 18Ni(300)steel and revealed how this microstructure influences austenite reversion upon aging.Segregation of Ti and Mo is experimentally detected at cell boundaries.It is interestingly found that a distinctive reverted austenite network forms rapidly along cell boundaries during aging,whereas much less austenite is found in conventionally treated 18Ni(300)steels.The rapid austenite reversion in SLM-fabricated material proceeds mainly via the growth of retained austenite on cell boundaries while the nucleation and growth of new austenite grains is negligible.Phase-field simulations suggest austenite grows in a fast,partitionless manner along cell boundaries where the chemical driving force for austen-ite reversion is substantially enhanced by Ti and Mo segregations,but in a sluggish,partitioning manner towards cell interiors.Contrary to conventional views that austenite fraction should be confined to avoid strength reduction,current SLM-fabricated 18Ni(300)steel containing∼13%cellular austenite is found to have higher tensile strength compared to its counterparts with negligible austenite.The design of austen-ite also shows its potential to enhance fracture toughness.The current study demonstrates that cellular structures could substantially alter austenite reversion behavior,providing a new route for microstructure architecting in additively manufactured steels.展开更多
In order to enhance the mechanical properties of the selective laser-melted(SLM) high-Mg content AlSiMg1.4 alloy,the Zr element was introduced.The influence of Zr alloying on the processability,microstructure,and mech...In order to enhance the mechanical properties of the selective laser-melted(SLM) high-Mg content AlSiMg1.4 alloy,the Zr element was introduced.The influence of Zr alloying on the processability,microstructure,and mechanical properties of the alloy was systematically investigated through performing microstructure analysis and tensile testing.It was demonstrated that the SLM-fabricated AlSiMg1.4-Zr alloy exhibited high process stability with a relative density of over 99.5% at various process parameters.Besides,the strong grain refinement induced by the primary Al3Zr particle during the melt solidification process simultaneously enhanced both the strength and plasticity of the alloy.The values for the yield strength,ultimate tensile strength,and elongation of the SLM-fabricated AlSiMg1.4-Zr were(343±3) MPa,(485±4) MPa,and(10.2±0.2)%,respectively,demonstrating good strengthplasticity synergy in comparison to the AlSiMg1.4 and other Al-Si-based alloys fabricated by SLM.展开更多
Oxygen is crucial in influencing the microstructure evolution of selective laser melted(SLMed)Ti–6Al–4V,significantly impacting its applicability in various sectors.Therefore,this study investigates the influnce of ...Oxygen is crucial in influencing the microstructure evolution of selective laser melted(SLMed)Ti–6Al–4V,significantly impacting its applicability in various sectors.Therefore,this study investigates the influnce of oxygen on microstructure evolution,particularlyα′martensite transformation and refinement mechanisms.Four alloys,Ti–6Al–4V–xO(x=0.11,0.16,0.21,and 0.25 wt%),were fabricated by the SLM process.The martensite start temperature(M_(s))of Ti–6Al–4V,as evaluated by computation,is 656.8°C,and oxygen was found to increase the M_(s) by about 10°C per 0.1 wt%.The SLMed alloy samples exhibit[001]_(β)growth texture along the build direction.Crystallographic analysis of martensite morphology suggests internal twinning on{1011}planes as the lattice invariant strain,which becomes more predominant with increasing oxygen content.Refinement of α′martensite plates by oxygen is due to increased lattice distortion,reduced prior β grain size,and oxygen segregation toβgrain boundaries.Our findings contribute to improving the understanding of the effect of oxygen on the transformation mechanism ofα′martensite during SLM of Ti–6Al–4V.展开更多
The relationships between the selective laser melting(SLM)processing parameters including laser power,scanning speed and hatch space,the relative density,the microstructure,and resulting mechanical properties of Ti-6A...The relationships between the selective laser melting(SLM)processing parameters including laser power,scanning speed and hatch space,the relative density,the microstructure,and resulting mechanical properties of Ti-6Al-2Zr-1Mo-1V alloy were investigated in this work.The result shows that laser power acts a dominant role in determining the relative density in comparison with scanning speed and hatch space.The optimal SLM process window for fabricating relative density>99%samples is located in the energy density range of 34.72 J·mm^(-3)to 52.08 J·mm^(-3),where the laser power range is between 125 W and 175 W.An upward trend is found in the micro-hardness as the energy density is increased.The optimum SLM processing parameters of Ti-6Al-2Zr-1Mo-1V alloy are:laser power of 150 W,scanning speed of 1,600 mm·s^(-1),hatch space of 0.08 mm,and layer thickness of 0.03 mm.The highest ultimate tensile strength,yield strength,and ductility under the optimum processing parameter are achieved,which are 1,205 MPa,1,099 MPa,and 8%,respectively.The results of this study can be used to guide SLM production Ti-6Al-2Zr-1Mo-1V alloy parts.展开更多
Cryogenic treatment was used to improve the tribological properties of Ti6Al4V artificial hip joint implants.Cryogenic treatment at-196℃with different holding time were carried out on Ti6Al4V specimens fabricated usi...Cryogenic treatment was used to improve the tribological properties of Ti6Al4V artificial hip joint implants.Cryogenic treatment at-196℃with different holding time were carried out on Ti6Al4V specimens fabricated using electron beam melting(EBM),and their microstructure and tribological properties evolution were systematically analyzed by scanning electron microscopy(SEM),vickers hardness,and wear tests.The experimental results show that the as-fabricated specimen consists of lamellarαphase andβcolumnar crystal.While,the thickness of lamellarαphase decreased after cryogenic treatment.In addition,it can be found that the fineαphase was precipitated and dispersed between the lamellarαphase with the holding time increase.Vickers hardness shows a trend of first increasing and then decreasing.The wear rate of the specimen cryogenic treated for 24 h is the minimum and the average friction coefficient is 0.50,which is reduced by 14.61%compared with the as-fabricated.The wear mechanism of the as-fabricated specimen is severe exfoliation,adhesive,abrasive,and slight fatigue wear.However,the specimen cryogenic treated for 24 h shows slight adhesive and abrasive wear.It can be concluded that it is feasibility of utilizing cryogenic treatment to reduce the wear of EBMed Ti6Al4V.展开更多
A new Al−4.87Mn−1.42Mg−0.63Sc−0.20Zr(wt.%)alloy was fabricated by selective laser melting(SLM)and its microstructure and mechanical properties before and after aging were investigated.The results show that at a laser ...A new Al−4.87Mn−1.42Mg−0.63Sc−0.20Zr(wt.%)alloy was fabricated by selective laser melting(SLM)and its microstructure and mechanical properties before and after aging were investigated.The results show that at a laser power input of 300 W,increasing laser scanning speeds from 700 to 1500 mm/s improves the mechanical properties.In the meantime,the lattice distortion values increase from 0.15%to 0.31%,showing an increasing solute supersaturation.At a laser scanning speed of 1500 mm/s,the yield strength,ultimate tensile strength and elongation of the as-SLM alloys are 356 MPa,412 MPa and 17.7%,respectively.After aging at 350°C for 8 h,these values increase to 527 MPa,554 MPa and 10.4%,respectively.The contributions to the yield strength increments from the secondary Al6(Fe,Mn)needle-like phase and re-precipitated L12 structured Al6(Sc,Zr,Ti)nano-particles during aging are 74 and 79 MPa,respectively.As the aging temperature increases to 450°C,the dominant precipitation strengthening is attributed to the secondary Al6(Sc,Zr,Ti)nano-particles.展开更多
In order to increase the processability and process window of the selective laser melting(SLM)-fabricated Al−Mn−Mg−Er−Zr alloy,a novel Si-modified Al−Mn−Mg−Er−Zr alloy was designed.The effect of Si alloying on the sur...In order to increase the processability and process window of the selective laser melting(SLM)-fabricated Al−Mn−Mg−Er−Zr alloy,a novel Si-modified Al−Mn−Mg−Er−Zr alloy was designed.The effect of Si alloying on the surface quality,processability,microstructure,and mechanical properties of the SLM-fabricated alloy was studied.The results showed that introducing Si into the Al−Mn−Mg−Er−Zr alloy prevented balling and keyhole formation,refined the grain size,and reduced the solidification temperature,which eliminated cracks and increased the processability and process window of the alloy.The maximum relative density of the SLM-fabricated Si/Al−Mn−Mg−Er−Zr alloy reached 99.6%.The yield strength and ultimate tensile strength of the alloy were(371±7)MPa and(518±6)MPa,respectively.These values were higher than those of the SLM-fabricated Al−Mn−Mg−Er−Zr and other Sc-free Al−Mg-based alloys.展开更多
Selective laser melting(SLM)has attracted great attention in the fabrication of magnesium-based biodegradable implants.However,current SLMed magnesium alloys are generally suffered from rapid corrosion,which is deadly...Selective laser melting(SLM)has attracted great attention in the fabrication of magnesium-based biodegradable implants.However,current SLMed magnesium alloys are generally suffered from rapid corrosion,which is deadly detrimental to their use.Herein,we thoroughly revealed why they are so vulnerable to corrosion through a typical SLMed AZ91D material model.An abnormally spatiotemporal“bulk erosion”mechanism was found,not the well-known“surface corrosion”mode of traditionally plastic-deformed alloys.The unique microstructure derived from SLM possesses high chemical reactivity,which is favorable for interactional attacks of fast fluid penetration,severe local corrosion and intensive micro-galvanic corrosion.Thus,it brings two orders of magnitude in corrosion rates compared with its plastic-deformed counterparts.In vitro,such fast-corrosion induced apparent cytotoxicity,cell damage,and further apoptosis to rat and mouse derived mesenchymal stem cells.In vivo,the material disintegrates into small pieces in a short period,and results in unexpected bone destruction and long-lasting foreign body reactions in Sprague Dawley rats.Close attention should be paid to this issue before SLMed Mg-based implants being applied in patients.展开更多
Mercury（Hg） in the Arctic is a significant concern due to its bioaccumulative and neurotoxic properties, and the sensitivity of Arctic environments. Previous research has found high levels of Hg in snowpacks with hi...Mercury（Hg） in the Arctic is a significant concern due to its bioaccumulative and neurotoxic properties, and the sensitivity of Arctic environments. Previous research has found high levels of Hg in snowpacks with high chloride（Cl-） concentrations. We hypothesised that Cl- would increase Hg retention by decreasing Hg photoreduction to Hg（0） in melted Arctic snow. To test this, changes in Hg photoreduction kinetics in melted Alert, NU snow were quantified with changing Cl- concentration and UV intensity. Snow was collected and melted in Teflon bottles in May 2014, spiked with 0–10 μg/g Cl-, and irradiated with 3.52–5.78 W·m-2 UV（280–400 nm）radiation in a Luz Chem photoreactor. Photoreduction rate constants（k）（0.14–0.59 hr-1） had positive linear relationships with [Cl-], while photoreduced Hg amounts（Hg（Ⅱ）red） had negative linear relationships with [Cl-]（1287–64 pg in 200 g melted snow）. Varying UV and[Cl-] both altered Hg（Ⅱ）red amounts, with more efficient Hg stabilisation by Cl- at higher UV intensity, while k can be predicted by Cl- concentration and/or UV intensity, depending on experimental parameters. Overall, with future projections for greater snowpack Cl- loading,our experimental results suggest that more Hg could be delivered to Arctic aquatic ecosystems by melted snow（smaller Hg（Ⅱ）red expected）, but the Hg in the melted snow that is photoreduced may do so more quickly（larger k expected）.展开更多
To develop large-scale RP systems used to producing functional parts and large-sized models has become an urgentcall now. In this paper, a large-scale RP system, MEM600-l, based on the melted extrusion manufacturing (...To develop large-scale RP systems used to producing functional parts and large-sized models has become an urgentcall now. In this paper, a large-scale RP system, MEM600-l, based on the melted extrusion manufacturing (MEM)process has been developed successfully. And the key issues to develop such a system are discussed. Based on theactual forming experiment, it is concluded that the MEM600-l works reliably and the forming efficiency is muchhigher than its parallel equipments.展开更多
The characteristics of some elements in inoculant were analyzed.The effect of the morphology of instantaneous inoculant on its melting velocity was studied.When the inoculants pass through the same sieve number,the vo...The characteristics of some elements in inoculant were analyzed.The effect of the morphology of instantaneous inoculant on its melting velocity was studied.When the inoculants pass through the same sieve number,the volume and the ratio of surface area to volume are different.It is evident from the theoretical analysis and experiment under some conditions that the melting velocity of inoculant depends on the morphology of inoculant.The morphology of inoculant during production should be controlled carefully.展开更多
Irregular grains, high interfacial stresses and anisotropic properties widely exist in 3D-printed metallic materials, and this paper investigated the effects of heat treatment on the microstructural, mechanical and co...Irregular grains, high interfacial stresses and anisotropic properties widely exist in 3D-printed metallic materials, and this paper investigated the effects of heat treatment on the microstructural, mechanical and corrosion properties of 316 L stainless steel fabricated by selective laser melting. Sub-grains and low-angle boundaries exist in the as-received selective laser melted(SLMed) 316 L stainless steel. After heat treatment at 1050℃, the sub-grains and low-angle boundaries changed slightly, and the stress state and strength decreased to some extent due to the decrease of dislocation density. After heat treatment at 1200℃, the grains became uniform, and the dislocation cells vanished, which led to a sharp decline in the hardness and strength. However, the ductility was improved after recrystallization heat treatment.The passive film thickness and corrosion potential of the SLMed 316 L stainless steel decreased after heat treatment, and the pitting potential also decreased due to the accelerated transition from metastable to steady-state pitting;this accelerated transition was caused by the presence of weak passive films at the enlarged pores after heat treatment, especially for an adequate solid solution treatment.展开更多
Laser welding is a promising process for joining small components produced by selective laser melting (SLM) to fabricate the large-scale and complex-shaped parts. In the work, the morphology, microstructure, microhard...Laser welding is a promising process for joining small components produced by selective laser melting (SLM) to fabricate the large-scale and complex-shaped parts. In the work, the morphology, microstructure, microhardness, tensile properties and corrosion resistance of the laser welded stress-relieved SLMed 304 stainless steel joints are investigated, as the different sections of stress-relieved SLMed 304 stainless steel are joined. Results show that the SLMed 304 stainless steel plates have a good laser weldability. The microstructure of laser-welded joints consists of the cellular dendrites in austenite matrix within columnar grains, exhibiting a coarser dendrite structure, lower microhardness (~220HV) and tensile properties (tensile strength of ~750 MPa, and area reduction of ~27.6%), but superior corrosion resistance to those of SLMed plates. The dendrite arm spacing of the joints varies from ~3.7μm in center zone, to ~5.0 (xm in fusion zone, to ~2.5 in epitaxial zone. The SLMed anisotropy shows a negligible effect on the microstructure and performance of the laser-welded joints. The laser welding along the building directions of the SLMed base plates can induce a slightly finer dendritic structure and higher tensile properties.展开更多
基金supported by the National Key Research and Development Program of China(No.2022YFC2406000)the Guangdong Basic and Applied Basic Research Foundation(2024A1515011024)+5 种基金the Guangzhou Science and Technology Project(2024A04J4943)the Guangdong Academy of Sciences Development Special Fund Project(2022GDASZH-2022010107)the Guangdong province Science and Technology Plan Projects(2023B1212120008,2023B1212060045)the GDAS Projects of International cooperation platform of Science and Technology(2022GDASZH-2022010203-003)Special Support Foundation of Guangdong Province(2023TQ07Z559)Shenzhen Basic Research Project(JCYJ20210324120001003 and JCYJ20220531091802006)。
文摘To clarify the densification behavior,deformation response and strengthening mechanisms of selective laser melted(SLM)Mg-RE alloys,this study systematically investigates a representative WE43 alloy via advanced material characterization techniques.A suitable laser output mode fell into the transition mode,allowing for the fabrication of nearly full-density samples(porosity=0.85±0.021%)with favorable mechanical properties(yield strength=351 MPa,ultimate tensile strength=417 MPa,the elongation at break=6.5%and microhardness=137.9±6.15 HV_(0.1))using optimal processing parameters(P=80 W,v=250 mm/s and d=50μm).Viscoplastic self-consistent analysis and transmission electron microscopy observations reveal that the plastic deformation response of the SLM Mg-RE alloys is primarily driven by basal and prismatic slips.Starting from a random texture before deformation(maximum multiple of ultimate density,Max.MUD=3.95),plastic stretching led the grains to align with the Z-axis,finally resulting in a{0001}<1010>texture orientation after fracture(Max.MUD=8.755).Main phases of the SLM state are mainly composed ofα-Mg,Mg_(24)Y_(5) andβ'-Mg_(41)Nd_(5),with an average grain size of only 4.27μm(about a quarter of that in the extruded state),resulting in a favorable strength-toughness ratio.Except for the nano-β'phase and semi-coherent Mg_(24)Y_(5) phase(mismatch=16.12%)around the grain boundaries,a small amount of nano-ZrO_(2) and Y_(2)O_(3) particles also play a role in dispersion strengthening.The high mechanical properties of the SLM state are chiefly attributed to precipitation hardening(44.41%),solid solution strengthening(34.06%)and grain boundary strengthening(21.53%),with precipitation hardening being predominantly driven by dislocation strengthening(67.77%).High-performance SLM Mg-RE alloy components were manufactured and showcased at TCT Asia 2024,receiving favorable attention.This work underscores the significant application potential of SLM Mg-RE alloys and establishes a strong foundation for advancing their use in the biomedical fields.
基金supported by the National Natural Science Foundation of China(NSFC)under Grant Nos.U24A2037,52130002,52321001.
文摘The effects of various heat treatments on the microstructures and mechanical properties of as-built selective laser melted Inconel 718 alloy were investigated through conventional and quasi-in-situ tensile tests.The corresponding heat treatment processes include direct aging(DA),solution+aging(SA),and homogenization+aging(HA).The DA and SA samples preserve the melt pool configuration and grain size stability,while the precipitated phase characteristics reveal the refinement of the long-strip Laves phase and the appearance of theδphase,respectively.The HA process induces recrystallization and grain coarsening.The specimens exhibit enhanced strength concomitant with diminished elongation,which is likely attributed to the reduction of the geometrically necessary dislocation density and the intensified precipitation of theγ′′phase after heat treatment.Tensile plastic deformation displays notable strain concentration along grain boundaries.The dimensional alterations in precipitated phases were measured to quantitatively determine the impact of grain boundary,dislocation and precipitation strengthening on the yield strength after heat treatment.Precipitation strengthening encompasses coherent,order,and Orowan strengthening.A remarkable agreement is revealed between theoretical predictions and experimental results.Insights are offered for optimizing heat treatment processes to comprehend microstructural evolution effect on the mechanical properties of additive-manufactured metals.
基金financially supported by the National Natural Science Foundation of China(No.12262014).
文摘A gradient nanostructured layer was fabricated on the surface of TA15(Ti-6Al-2Zr-1Mo-1V)alloy(produced by selective laser melting)using severe shot peening(SSP).This study focuses on the evolution of the microstructure and the mechanism of grain refinement in TA15 titanium alloy during SSP treatment.Transmission electron microscopyand Rietveld refinement methods were employed.The residual stress and microhardness variations with depth were also characterized.The results show:(1)At the initial stage of deformation,plastic deformation is primarily accommodated through twinning and dislocation slip.(2)As the strain increases,twinning disappears,and dislocations interact to form tangles.Some dislocations annihilate and rearrange into subgrain boundaries,subdividing the original grains into subgrains.(3)With continued dislocation activity,the subgrain size decreases until nanocrystals are formed through the dynamic rotational recrystallization.SSP introduced compressive residual stress(CRS)in the near-surface layer of the material,with the maximum CRS of approximately−1141 MPa observed in the subsurface layer.It also induced work hardening,increasing the surface hardness to approximately 479 HV.However,the surface roughness increases,leading to a slight deterioration in surface quality.
文摘In the original publication,mistakenly first and corresponding affiliation is given as:Thermoelectricity Technology Center,Hangzhou Dahe Thermo-Magnetics Co.Ltd,Hangzhou 310053,ChinaThe correct first and corresponding affiliation is:State Key Laboratory of Silicon Materials,School of Materials Science and Engineering,Zhejiang University,Hangzhou 310027,China.
基金financially supported by the National Key Research and Development Program of China(No.2021YFB3702501)the National Science and Technology Major Project(J2019-VI-0019-0134).
文摘Selective laser melting(SLM)has become a critical technique for manufacturing molds with conformal cooling channels to achieve high cooling efficiencies.A novel selective laser-melted 718HH plastic mold steel with an excellent combination of strength and toughness was investigated.After SLM fabrication,quenching and tempering are conducted as post-printing heat treatment(PPHT)to improve the mechanical properties of the as-built samples.Both the microstructure and the corresponding mechanical properties were systematically studied.The results show that PPHT facilitates the complete martensite transformation.Meanwhile,the retained austenite(γ)phase was still found in the as-built samples.And high-density dislocations were dispersively distributed within the martensite matrix for both as-built and as-PPHTed samples.After PPHT,due to the recovery and recrystallization of martensite,reduced dislocation density and increased high-angle grain boundaries,the microhardness of the as-built samples decreased from 498.8±16.7 to 382.1±5.0 HV0.3.Correspondingly,the strength,including the ultimate tensile strength and yield strength,of the as-built and as-PPHTed samples also decreased from 1411.3±17.8 to 1208.7±3.2 MPa and 1267.3±11.7 to 1084.7±5.1 MPa,respectively.On the contrary,the value of impact energy significantly increased from 15.3±1.2 J(as-built)to 39.7±1.2 J(as-PPHTed).Notably,the mechanical properties of SLMed 718HH samples are significantly better than those of corresponding wrought samples.
基金supported by the Pazy Foundation of the Israel Atomic Energy Commission and the Israeli Council of Higher Education(Grant No.322/20)。
文摘Only a few studies have reported the efects of electrochemical hydrogenation on the tensile mechanical properties of additively manufactured Ti–6Al–4V alloy,in all of them the alloy was processed by laser powder-bed fusion.Furthermore,the efects of either hot isostatic pressing(HIP)or heat treatment(HT)post-treatments on the mechanical properties were not reported.Here,the Young’s modulus,ultimate tensile stress,and uniform(homogeneous)strain of as-built electron beam melted(EBM)Ti–6Al–4V alloys were studied using small tensile specimens before and after electrochemical hydrogenation,as well as before and after secondary processes of HIP at 920℃ and HT at 1000℃.The tensile properties of all hydrogenated alloys were signifcantly degraded compared to their non-hydrogenated counterparts.The yield stress could not be determined for all hydrogenated alloys,as failure occurred at a strain below 0.2%ofset.The uniform strain of the hydrogenated alloys was less than 1%,compared to 1%–5%for the non-hydrogenated alloys.The fracture mode of the hydrogenated alloys after HIP and HT revealed cleavage fracture,indicating increased brittleness.In the as-built hydrogenated alloy,the fracture mode varied with location:brittle fracture occurred near the surface due to the formation of a hydride layer,while a more ductile fracture with dimples was observed below this layer.
基金supported by the National Natural Science Foundation of China(Nos.51801079,52001140)the National Funds Through FCT of Portugal–Fundacao para a Ciência e a Tecnologia,under a scientific contract of 2021.04115.CEECIND,and the Projects of UIDB/00285/2020,and LA/0112/2020。
文摘To improve the processability and mechanical properties of the selective laser melting(SLM)low Sc content Al−Mg−Sc−Zr alloy,Mn was used to partially replace Mg.The processability,microstructure,and mechanical properties of the SLM-fabricated Al−Mg−Mn−Sc−Zr alloy were systematically investigated by density measurement,microstructure characterization,and tensile testing.The results revealed that dense samples could be obtained by adjusting the SLM process parameters.The alloy exhibited a fine equiaxed-columnar bimodal grain microstructure.The presence of primary Al3Sc andα-Al(Mn,Fe)Si particles contributed to the grain refinement of the alloy with an average grain size of 4.63μm.Upon aging treatment at 350°C for 2 h,the strength and elongation of the alloy were simultaneously improved due to the precipitation of Al3Sc nanoparticles and the formation of the 9R phase.This study demonstrates that the strength−plasticity trade-off of the aluminum alloy can be overcome by utilizing SLM technology and subsequent post-heat treatment to induce the formation of the long-period stacked ordered phase.
基金the National Key R&D program of China(Grant Nos.2022YFB3705200 and 2021YFB3702301)the National Natural Science Foundation of China(Grant No.52171008)+2 种基金the National Key R&D program of China(Grant No.2022YFE0110800)the National Natural Science Foundation of China(Grants Nos.51922054 and U1808208)the Mobility Programme from the Sino-German Center(Grant No.M-0319).
文摘Cellular microstructure is a unique feature in alloys fabricated by selective laser melting(SLM).Abundant efforts have been made to reveal the formation mechanism of cellular microstructures and its influences on mechanical performances,while its potential role in microstructure architecting during post-heat treatment is rarely explored.In this work,we investigated the features of cellular microstructures in an SLM-fabricated 18Ni(300)steel and revealed how this microstructure influences austenite reversion upon aging.Segregation of Ti and Mo is experimentally detected at cell boundaries.It is interestingly found that a distinctive reverted austenite network forms rapidly along cell boundaries during aging,whereas much less austenite is found in conventionally treated 18Ni(300)steels.The rapid austenite reversion in SLM-fabricated material proceeds mainly via the growth of retained austenite on cell boundaries while the nucleation and growth of new austenite grains is negligible.Phase-field simulations suggest austenite grows in a fast,partitionless manner along cell boundaries where the chemical driving force for austen-ite reversion is substantially enhanced by Ti and Mo segregations,but in a sluggish,partitioning manner towards cell interiors.Contrary to conventional views that austenite fraction should be confined to avoid strength reduction,current SLM-fabricated 18Ni(300)steel containing∼13%cellular austenite is found to have higher tensile strength compared to its counterparts with negligible austenite.The design of austen-ite also shows its potential to enhance fracture toughness.The current study demonstrates that cellular structures could substantially alter austenite reversion behavior,providing a new route for microstructure architecting in additively manufactured steels.
基金supported by the National Natural Science Foundation of China (Nos.51801079, 52001140)。
文摘In order to enhance the mechanical properties of the selective laser-melted(SLM) high-Mg content AlSiMg1.4 alloy,the Zr element was introduced.The influence of Zr alloying on the processability,microstructure,and mechanical properties of the alloy was systematically investigated through performing microstructure analysis and tensile testing.It was demonstrated that the SLM-fabricated AlSiMg1.4-Zr alloy exhibited high process stability with a relative density of over 99.5% at various process parameters.Besides,the strong grain refinement induced by the primary Al3Zr particle during the melt solidification process simultaneously enhanced both the strength and plasticity of the alloy.The values for the yield strength,ultimate tensile strength,and elongation of the SLM-fabricated AlSiMg1.4-Zr were(343±3) MPa,(485±4) MPa,and(10.2±0.2)%,respectively,demonstrating good strengthplasticity synergy in comparison to the AlSiMg1.4 and other Al-Si-based alloys fabricated by SLM.
基金financially supported by the National Natural Science Foundation of China(No.52205431)the CAS Interdisciplinary Innovation Team Project(No.JCTD-2020-10)。
文摘Oxygen is crucial in influencing the microstructure evolution of selective laser melted(SLMed)Ti–6Al–4V,significantly impacting its applicability in various sectors.Therefore,this study investigates the influnce of oxygen on microstructure evolution,particularlyα′martensite transformation and refinement mechanisms.Four alloys,Ti–6Al–4V–xO(x=0.11,0.16,0.21,and 0.25 wt%),were fabricated by the SLM process.The martensite start temperature(M_(s))of Ti–6Al–4V,as evaluated by computation,is 656.8°C,and oxygen was found to increase the M_(s) by about 10°C per 0.1 wt%.The SLMed alloy samples exhibit[001]_(β)growth texture along the build direction.Crystallographic analysis of martensite morphology suggests internal twinning on{1011}planes as the lattice invariant strain,which becomes more predominant with increasing oxygen content.Refinement of α′martensite plates by oxygen is due to increased lattice distortion,reduced prior β grain size,and oxygen segregation toβgrain boundaries.Our findings contribute to improving the understanding of the effect of oxygen on the transformation mechanism ofα′martensite during SLM of Ti–6Al–4V.
基金supported by Liaoning Doctoral Research Start-up Fund project(Grant No.2023-BS-215).
文摘The relationships between the selective laser melting(SLM)processing parameters including laser power,scanning speed and hatch space,the relative density,the microstructure,and resulting mechanical properties of Ti-6Al-2Zr-1Mo-1V alloy were investigated in this work.The result shows that laser power acts a dominant role in determining the relative density in comparison with scanning speed and hatch space.The optimal SLM process window for fabricating relative density>99%samples is located in the energy density range of 34.72 J·mm^(-3)to 52.08 J·mm^(-3),where the laser power range is between 125 W and 175 W.An upward trend is found in the micro-hardness as the energy density is increased.The optimum SLM processing parameters of Ti-6Al-2Zr-1Mo-1V alloy are:laser power of 150 W,scanning speed of 1,600 mm·s^(-1),hatch space of 0.08 mm,and layer thickness of 0.03 mm.The highest ultimate tensile strength,yield strength,and ductility under the optimum processing parameter are achieved,which are 1,205 MPa,1,099 MPa,and 8%,respectively.The results of this study can be used to guide SLM production Ti-6Al-2Zr-1Mo-1V alloy parts.
基金Funded by the National Natural Science Foundation of China(No.42102345)the Fundamental Research Funds for the Central Universities(No.2023ZKPYJD03)。
文摘Cryogenic treatment was used to improve the tribological properties of Ti6Al4V artificial hip joint implants.Cryogenic treatment at-196℃with different holding time were carried out on Ti6Al4V specimens fabricated using electron beam melting(EBM),and their microstructure and tribological properties evolution were systematically analyzed by scanning electron microscopy(SEM),vickers hardness,and wear tests.The experimental results show that the as-fabricated specimen consists of lamellarαphase andβcolumnar crystal.While,the thickness of lamellarαphase decreased after cryogenic treatment.In addition,it can be found that the fineαphase was precipitated and dispersed between the lamellarαphase with the holding time increase.Vickers hardness shows a trend of first increasing and then decreasing.The wear rate of the specimen cryogenic treated for 24 h is the minimum and the average friction coefficient is 0.50,which is reduced by 14.61%compared with the as-fabricated.The wear mechanism of the as-fabricated specimen is severe exfoliation,adhesive,abrasive,and slight fatigue wear.However,the specimen cryogenic treated for 24 h shows slight adhesive and abrasive wear.It can be concluded that it is feasibility of utilizing cryogenic treatment to reduce the wear of EBMed Ti6Al4V.
基金supported by the Science and Technology Innovation Program of Hunan Province,China(No.2023RC3055)the Natural Science Foundation of Hunan Province,China(Nos.2023JJ30671)+1 种基金the Natural Science Foundation of Changsha City,China(No.Kq2208264)the National Natural Science Foundation of China(No.51601229).
文摘A new Al−4.87Mn−1.42Mg−0.63Sc−0.20Zr(wt.%)alloy was fabricated by selective laser melting(SLM)and its microstructure and mechanical properties before and after aging were investigated.The results show that at a laser power input of 300 W,increasing laser scanning speeds from 700 to 1500 mm/s improves the mechanical properties.In the meantime,the lattice distortion values increase from 0.15%to 0.31%,showing an increasing solute supersaturation.At a laser scanning speed of 1500 mm/s,the yield strength,ultimate tensile strength and elongation of the as-SLM alloys are 356 MPa,412 MPa and 17.7%,respectively.After aging at 350°C for 8 h,these values increase to 527 MPa,554 MPa and 10.4%,respectively.The contributions to the yield strength increments from the secondary Al6(Fe,Mn)needle-like phase and re-precipitated L12 structured Al6(Sc,Zr,Ti)nano-particles during aging are 74 and 79 MPa,respectively.As the aging temperature increases to 450°C,the dominant precipitation strengthening is attributed to the secondary Al6(Sc,Zr,Ti)nano-particles.
基金the National Natural Science Foundation of China(Nos.51801079,52001140)the Portugal National Funds through FCT Project(No.2021.04115).
文摘In order to increase the processability and process window of the selective laser melting(SLM)-fabricated Al−Mn−Mg−Er−Zr alloy,a novel Si-modified Al−Mn−Mg−Er−Zr alloy was designed.The effect of Si alloying on the surface quality,processability,microstructure,and mechanical properties of the SLM-fabricated alloy was studied.The results showed that introducing Si into the Al−Mn−Mg−Er−Zr alloy prevented balling and keyhole formation,refined the grain size,and reduced the solidification temperature,which eliminated cracks and increased the processability and process window of the alloy.The maximum relative density of the SLM-fabricated Si/Al−Mn−Mg−Er−Zr alloy reached 99.6%.The yield strength and ultimate tensile strength of the alloy were(371±7)MPa and(518±6)MPa,respectively.These values were higher than those of the SLM-fabricated Al−Mn−Mg−Er−Zr and other Sc-free Al−Mg-based alloys.
基金supported by the National Natural Science Foundation of China(Nos.52101283 and U22A20121)the National Key R&D Program of China(Nos.2021YFC2400700 and 2022YFC2406000)+6 种基金the Science and Technology Planning Project of Guangzhou(No.202201011454)the NSFC Incubation Program of GDPH(No.KY012021165)the High-level Hospital Construction Project(No.KJ012019520)the Special Fund Project of Guangdong Academy of Sciences(Nos.2022GDASZH-2022010107 and 2021GDASYL-20210102005)the GDAS Projects of International Cooperation Platform of Science and Technology(No.2022GDASZH-2022010203-003)the Guangdong Basic and Applied Basic Research Foundation(No.2022B1515250004)the Young Elite Scientist Sponsorship Program by China Association for Science and Technology(CAST)(No.YESS20210269).
文摘Selective laser melting(SLM)has attracted great attention in the fabrication of magnesium-based biodegradable implants.However,current SLMed magnesium alloys are generally suffered from rapid corrosion,which is deadly detrimental to their use.Herein,we thoroughly revealed why they are so vulnerable to corrosion through a typical SLMed AZ91D material model.An abnormally spatiotemporal“bulk erosion”mechanism was found,not the well-known“surface corrosion”mode of traditionally plastic-deformed alloys.The unique microstructure derived from SLM possesses high chemical reactivity,which is favorable for interactional attacks of fast fluid penetration,severe local corrosion and intensive micro-galvanic corrosion.Thus,it brings two orders of magnitude in corrosion rates compared with its plastic-deformed counterparts.In vitro,such fast-corrosion induced apparent cytotoxicity,cell damage,and further apoptosis to rat and mouse derived mesenchymal stem cells.In vivo,the material disintegrates into small pieces in a short period,and results in unexpected bone destruction and long-lasting foreign body reactions in Sprague Dawley rats.Close attention should be paid to this issue before SLMed Mg-based implants being applied in patients.
基金provided by the NSERC Discovery grant # 341960-2013Canada Research Chairs Program to N.O. Scholarships to Erin Mann from NSERC CREATE and Memorial University of Newfoundland
文摘Mercury（Hg） in the Arctic is a significant concern due to its bioaccumulative and neurotoxic properties, and the sensitivity of Arctic environments. Previous research has found high levels of Hg in snowpacks with high chloride（Cl-） concentrations. We hypothesised that Cl- would increase Hg retention by decreasing Hg photoreduction to Hg（0） in melted Arctic snow. To test this, changes in Hg photoreduction kinetics in melted Alert, NU snow were quantified with changing Cl- concentration and UV intensity. Snow was collected and melted in Teflon bottles in May 2014, spiked with 0–10 μg/g Cl-, and irradiated with 3.52–5.78 W·m-2 UV（280–400 nm）radiation in a Luz Chem photoreactor. Photoreduction rate constants（k）（0.14–0.59 hr-1） had positive linear relationships with [Cl-], while photoreduced Hg amounts（Hg（Ⅱ）red） had negative linear relationships with [Cl-]（1287–64 pg in 200 g melted snow）. Varying UV and[Cl-] both altered Hg（Ⅱ）red amounts, with more efficient Hg stabilisation by Cl- at higher UV intensity, while k can be predicted by Cl- concentration and/or UV intensity, depending on experimental parameters. Overall, with future projections for greater snowpack Cl- loading,our experimental results suggest that more Hg could be delivered to Arctic aquatic ecosystems by melted snow（smaller Hg（Ⅱ）red expected）, but the Hg in the melted snow that is photoreduced may do so more quickly（larger k expected）.
基金The author would like to acknowledge the support by the National Natural Science Foundation of China (Grant No. 50105006)and the support by the 985 Foundation of Tsinghua University,Beijing, China.
文摘To develop large-scale RP systems used to producing functional parts and large-sized models has become an urgentcall now. In this paper, a large-scale RP system, MEM600-l, based on the melted extrusion manufacturing (MEM)process has been developed successfully. And the key issues to develop such a system are discussed. Based on theactual forming experiment, it is concluded that the MEM600-l works reliably and the forming efficiency is muchhigher than its parallel equipments.
文摘The characteristics of some elements in inoculant were analyzed.The effect of the morphology of instantaneous inoculant on its melting velocity was studied.When the inoculants pass through the same sieve number,the volume and the ratio of surface area to volume are different.It is evident from the theoretical analysis and experiment under some conditions that the melting velocity of inoculant depends on the morphology of inoculant.The morphology of inoculant during production should be controlled carefully.
基金supported financially by the National Key Research and Development Program of China (No. 2017YFB 0702300)the National Natural Science Foundation of China (No. 51671029)the Fundamental Research Funds for the Central Universities (No. FRF-TP-17-002B)
文摘Irregular grains, high interfacial stresses and anisotropic properties widely exist in 3D-printed metallic materials, and this paper investigated the effects of heat treatment on the microstructural, mechanical and corrosion properties of 316 L stainless steel fabricated by selective laser melting. Sub-grains and low-angle boundaries exist in the as-received selective laser melted(SLMed) 316 L stainless steel. After heat treatment at 1050℃, the sub-grains and low-angle boundaries changed slightly, and the stress state and strength decreased to some extent due to the decrease of dislocation density. After heat treatment at 1200℃, the grains became uniform, and the dislocation cells vanished, which led to a sharp decline in the hardness and strength. However, the ductility was improved after recrystallization heat treatment.The passive film thickness and corrosion potential of the SLMed 316 L stainless steel decreased after heat treatment, and the pitting potential also decreased due to the accelerated transition from metastable to steady-state pitting;this accelerated transition was caused by the presence of weak passive films at the enlarged pores after heat treatment, especially for an adequate solid solution treatment.
基金supported financially by the Pre-research Fund Project of Ministry of Equipment and Development of China (No. 61409230301)the Fundamental Research Funds for the Central Universities (No. HUST: 2016YXZD005)+1 种基金the National Natural Science Foundation of China (No. 51805186)the China Postdoctoral Science Foundation Funded Project (Nos. 2017M620317 and 2018T110759)
文摘Laser welding is a promising process for joining small components produced by selective laser melting (SLM) to fabricate the large-scale and complex-shaped parts. In the work, the morphology, microstructure, microhardness, tensile properties and corrosion resistance of the laser welded stress-relieved SLMed 304 stainless steel joints are investigated, as the different sections of stress-relieved SLMed 304 stainless steel are joined. Results show that the SLMed 304 stainless steel plates have a good laser weldability. The microstructure of laser-welded joints consists of the cellular dendrites in austenite matrix within columnar grains, exhibiting a coarser dendrite structure, lower microhardness (~220HV) and tensile properties (tensile strength of ~750 MPa, and area reduction of ~27.6%), but superior corrosion resistance to those of SLMed plates. The dendrite arm spacing of the joints varies from ~3.7μm in center zone, to ~5.0 (xm in fusion zone, to ~2.5 in epitaxial zone. The SLMed anisotropy shows a negligible effect on the microstructure and performance of the laser-welded joints. The laser welding along the building directions of the SLMed base plates can induce a slightly finer dendritic structure and higher tensile properties.
