Copper manufactured by laser powder bed fusion(LPBF)process typically exhibits poor strength-ductility coordination,and the addition of strengthening phases is an effective way to address this issue.To explore the eff...Copper manufactured by laser powder bed fusion(LPBF)process typically exhibits poor strength-ductility coordination,and the addition of strengthening phases is an effective way to address this issue.To explore the effects of strengthening phases on Cu,Cu-carbon nanotubes(CNTs)composites were prepared using LPBF technique with Cu-CNTs mixed powder as the matrix.The formability,microstructure,mechanical properties,electrical conductivity,and thermal properties were studied.The result shows that the prepared composites have high relative density.The addition of CNTs results in inhomogeneous equiaxed grains at the edges of the molten pool and columnar grains at the center.Compared with pure copper,the overall mechanical properties of the composite are improved:tensile strength increases by 52.8%and elongation increases by 146.4%;the electrical and thermal properties are also enhanced:thermal conductivity increases by 10.8%and electrical conductivity increases by 12.7%.展开更多
In this study,carbon nanotubes(CNTs)/AlSi10Mg composite parts with CNTs contents ranging from 0.0 to 2.0wt.%were successfully fabricated via laser powder bed fusion(LPBF)with laser scan speeds ranging from 900 to 1,90...In this study,carbon nanotubes(CNTs)/AlSi10Mg composite parts with CNTs contents ranging from 0.0 to 2.0wt.%were successfully fabricated via laser powder bed fusion(LPBF)with laser scan speeds ranging from 900 to 1,900 mm·s^(-1).Uniform dispersion of CNTs in the powders can be achieved when their content is below 2.0wt.%.In the LPBF samples,the morphology of the CNTs is found to be directly related to their content.Especially,the length of CNTs in samples prepared by LPBF increases as the CNT content increases.The length of CNTs is approximately 200-300 nm in the 1.0wt.%CNTs/AlSi10Mg composites and approximately 500-1,000 nm in the 2.0wt.%CNTs/AlSi10Mg composites.The hardness of the composites reaches its highest value of 143.3 HV when the CNTs content is 1.0wt.%and the laser scan speed is 1,300 mm·s^(-1).It is found that the self-lubricating properties of the CNTs improve the tribological properties of the composites.The coefficient of friction(CoF)and wear rate of the samples decrease with increasing CNT content.At a CNTs content of 2.0wt.%,the CoF and wear rate of the composite decrease by approximately 14%and 30%,respectively,compared to the unreinforced matrix.The presence of CNTs leads to a more complete and refined network microstructure within the samples.Both the CNTs and the aluminum carbide contribute to the Orowan mechanism and the Hall-Petch effect within the matrix.展开更多
激光粉末床熔融(Laser Powder Bed Fusion,LPBF)是金属增材制造技术中的重要分支,具有个性化、自动化等优势。然而,在逐层制造过程中由于残余应力不断积累,易引发变形、断裂、疲劳等问题,限制了其进一步应用。为预测金属增材制造件的位...激光粉末床熔融(Laser Powder Bed Fusion,LPBF)是金属增材制造技术中的重要分支,具有个性化、自动化等优势。然而,在逐层制造过程中由于残余应力不断积累,易引发变形、断裂、疲劳等问题,限制了其进一步应用。为预测金属增材制造件的位移和残余应力,借助开源有限元求解代码JAX-FEM,开展基于热弹塑性本构模型的LPBF全尺寸热-力耦合数值模拟研究。其中,根据能量守恒定律确定等效激光功率、等效激光半径及扫描速度,简化计算模型、减少计算时间;通过修改制件底面的应力状态实现模拟制件从基板上切割分离的过程,并预测了应力释放的影响。分析扫描策略与速度对LPBF热-力耦合行为的影响,对比发现,采用水平Z形扫描策略相较于垂直扫描策略所产生的最大位移降低了24.0%,最大残余应力降低了13.6%;当扫描速度从0.8m/s增大到1.6m/s时,产生的最大位移降低了6.4%,最大残余应力降低了5.2%。该研究有助于为调控LPBF残余应力和变形提供科学指导。展开更多
Superelastic NiTi alloys produced through laser powder bed fusion(LPBF)hold great promise in advancing wear-resistant transmission devices for aerospace and related applications.However,limited research on their wear ...Superelastic NiTi alloys produced through laser powder bed fusion(LPBF)hold great promise in advancing wear-resistant transmission devices for aerospace and related applications.However,limited research on their wear behavior and strategies for enhancing wear resistance raises concerns about their future application prospects.In this study,a straightforward yet highly effective pre-strain treatment method is introduced,resulting in a nearly twofold improvement in the wear resistance of LPBF-fabricated NiTi alloys.This method prunes microstructure characteristics,influences the martensitic transformation process that improves cyclic compression superelasticity and transforms the distribution characteristics of adhesion stress acting on the indenter during wear processes,thereby effectively enhancing wear resistance.Additionally,the present study proposes an analytical model that establishes a link between superelastic metal cyclic compression characteristics and wear behaviors,providing insight into the wear characteristics,especially for adhesive wear patterns of superelastic metals including LPBF-fabricated NiTi alloys through analysis of cyclic compression curve.This research contributes to the fundamental understanding of wear resistance mechanisms in superelastic engineering materials and opens avenues for further optimization in related applications.展开更多
Silicon-based anodes,utilizing nanosized silicon materials,hold great promise for the next-generation of lithium-ion batteries due to their high capacity and stable expansion.This study aims to address challenges in t...Silicon-based anodes,utilizing nanosized silicon materials,hold great promise for the next-generation of lithium-ion batteries due to their high capacity and stable expansion.This study aims to address challenges in traditional slurry-coated anodes,such as agglomeration and low adhesive strength,through the application of laser powder bed fusion(LPBF).The process involves fabricating an Al-Si-Cu alloy layer on a Cu foil current collector,followed by dealloying to create a porous Si-Cu anode.Simulated and experimental results demonstrate successful alloy layer formation through optimized laser spot(55μm)and powder sizes(1-5μm).Controlled cooling produces primary Si particles ranging from 150 nm to 1μm.The resulting microstructure enhances electrochemical performance,particularly by tailoring the size of primary Si.The resultant porous Si-Cu anode,featuring uniformly distributed primary Si(200 nm)metallurgically bonded with Cu networks,exhibits an initial coulombic efficiency of 83% and a remarkable capacity retention of 80% after 300 cycles at 2 C.In-situ and ex-situ observations confirm the crucial role of anode architecture in performance enhancement.This study elucidates the influence of the LPBF microstructure on anode performance and broadens the potential application of laser powder bed fusion in battery manufacturing.展开更多
Based on the actual conditions of laser powder bed fusion(LPBF),a three-dimensional transient thermal-structural coupling single-layer finite element model was established to simulate the LPBF of Al-Cu-Mg-Si alloys.Af...Based on the actual conditions of laser powder bed fusion(LPBF),a three-dimensional transient thermal-structural coupling single-layer finite element model was established to simulate the LPBF of Al-Cu-Mg-Si alloys.After characterizing the thermal behavior and residual stress distribution of the molten pool under different LPBF parameters,the cracking mechanisms of the Al-Cu-Mg-Si alloy were revealed.With an increase in the number of scanning tracks,the maximum cooling rate decreased gradually,whereas the maximum heating rate first increased and then decreased.The residual stress of the printed parts after cooling was primarily tensile stress.The residual stress along the scanning direction was mainly distributed in the center of the printing layer,whereas the residual stress perpendicular to the scanning direction was mainly concentrated in the center of the track.The residual stress along the deposition direction decreased with increasing distance from the substrate,with the highest stress occurring at the contact position with the substrate.Compared with the scanning speed,the laser power had a greater effect on the temperature and residual stress.The reliability of the numerical simulation was verified based on the size of the molten pool and the direction of crack propagation.展开更多
WE43 is a high-strength magnesium alloy containing rare-earth elements such as Y,Gd and Nd.Nevertheless,how to further obtain the balance of strength and ductility,as well as the manufacture of complex structures is s...WE43 is a high-strength magnesium alloy containing rare-earth elements such as Y,Gd and Nd.Nevertheless,how to further obtain the balance of strength and ductility,as well as the manufacture of complex structures is still a dilemma for its engineering application.In this study,WE43 alloy samples withfine microstructures,high densification and excellent mechanical properties were successfully prepared by laser powder bed fusion(LPBF)additive manufacturing.The optimal process window was established,and the formation mechanisms of three types of porosity defects were revealed,namely lack-of-fusion pores,meltfluctuation-induced pores,and keyhole-induced pores.With the combined process of laser power of 200 W and scanning speed of 600 mm/s,samples with a high density of 99.89%were obtained.Furthermore,periodic heterogeneous microstructure was prepared along the build direction,i.e.,fine grains(∼4.1μm)at melt pool boundaries and coarse grain(∼23.6μm)inside melt pool.This was mainly due to the preferential precipitation of Zr and Mg_(3)(Gd,Nd)nano-precipitates at the melt pool boundaries providing nucleation sites for the grains.This special feature could provide an extra hetero-deformation induced(HDI)strengthening and retard fracture.The optimal tensile yield strength,ultimate tensile strength and elongation at break were 276±1 MPa,292±1 MPa and 6.1±0.2%,respectively.The obtained tensile properties were superior to those of other magnesium alloys and those fabricated by other processes.The solid solution strengthening(∼24.5%),grain boundary strengthening(∼14.4%)and HDI strengthening(∼32.2%)were the main sources of high yield strength.This work provides a guidance on studying the pore defect suppression and strengthening mechanisms of WE43 alloy and other magnesium alloys produced by LPBF.展开更多
As a universal casting Mg-RE alloy,Mg-6Gd-3Y-Zr(GW63K,wt.%)alloy exhibits superior strength-ductility synergy and holds significant potential for engineering applications.In this study,the GW63K alloy is produced usin...As a universal casting Mg-RE alloy,Mg-6Gd-3Y-Zr(GW63K,wt.%)alloy exhibits superior strength-ductility synergy and holds significant potential for engineering applications.In this study,the GW63K alloy is produced using the laser powder bed fusion(LPBF)additive manufacturing(AM)process for the first time.The printability,microstructure characteristics,and post-heat treatment conditions of the GW63K alloy are systematically investigated.The as-built GW63K samples demonstrate high relative densities exceeding 99.6%and exhibit no macroscopic and microscopic cracking across a wide range of process parameters,indicating excellent printability.An exceptional heterogeneous microstructure is observed in the as-built GW63K alloy,comprising coarse columnar grains,fine equiaxed grains with an average grain size of 21.72μm,uniformly distributed nano-sized Mg_(24)(Gd,Y)_(5)secondary phase,and numerous dislocations.Consequently,the as-built GW63K alloy displays enhanced tensile strengths and ductility compared to the as-cast alloy,with yield strength(YS),ultimate tensile strength(UTS)and elongation(EL)values of 218±4 MPa,284±5 MPa and 11.9±1.6%respectively.Additionally,due to the absence of coarse micron-sized secondary phase,a specific direct aging(T5)heat treatment regime at 200℃for 128 h is optimized for the as-built GW63K alloy to introduce dense and dispersedβ’aging precipitates.This T5 treatment surpasses the conventional solution plus aging(T6)heat treatment in enhancing mechanical properties.The LPBF-T5 GW63K alloy exhibits YS,UTS and EL values of 293±6 MPa,359±4 MPa and 2.9±0.7%,respectively.Notably,the YS of the LPBF-T5 alloy represents the highest value for the GW63K alloy,even surpassing that of the extrusion-T5 alloy.This study indicates that the GW63K alloy is a highly promising material for manufacturing near-net-shape high-strength Mg alloy components with intricate geometries using LPBF.展开更多
Poly-ether-ether-ketone/nano-silicon nitride(PEEK/nSN)composite scaffolds,fabricated by laser powder bed fusion(LPBF),show great potential for orthopedic applications due to their excellent biological performance and ...Poly-ether-ether-ketone/nano-silicon nitride(PEEK/nSN)composite scaffolds,fabricated by laser powder bed fusion(LPBF),show great potential for orthopedic applications due to their excellent biological performance and mechanical adaptability.However,the effect of nSN on LPBF processability and scaffold properties remains unclear.This study systematically investigates the processability and mechanical per-formance of PEEK/nSN composites to enable reliable clinical fabrication.The results show that adding nSN improves powder flowability and inhibits crystallization,enhancing LPBF processability.The introduction of nSN reduces PEEK’s non-isothermal crystallization Avrami exponent from 3.04 to 2.01,suggesting a transformation from a three-dimensional spherulitic to a two-dimensional lamellar crystal structure.Tensile tests reveal that the presence of nSN alters the optimal process parameters,reducing the optimal laser power from 25 W to 22 W due to increased energy absorption efficiency,as shown by an increase in absorbance at 843 cm^(-1)from 0.27 to 0.35 as the nSN content increases to 2 wt%.Porous diamond-structured scaffolds were fabricated using optimal parameters for pure PEEK,PEEK/1 wt%nSN,and PEEK/2 wt%nSN.Diamond-structured scaffolds fabricated with 1 wt%nSN showed a 12.2%increase in elastic modulus compared to pure PEEK,highlighting the enhanced mechanical performance.Over-all,this study offers key insights into the stable and customizable LPBF fabrication of PEEK/nSN porous scaffolds,providing a foundation for future research on their bioactivity and antibacterial properties for orthopedic applications.展开更多
The addition of ceramic reinforcements provides a promising approach to achieving high-performance magnesium matrix composites.In this work,AZ91D magnesium alloys and 2 wt.%TiC/AZ91D composites have been manufactured ...The addition of ceramic reinforcements provides a promising approach to achieving high-performance magnesium matrix composites.In this work,AZ91D magnesium alloys and 2 wt.%TiC/AZ91D composites have been manufactured by laser powder bed fusion(LPBF)with variations of laser processing parameters.The effect of TiC reinforcement addition on the laser absorption behaviors,forming quality,microstructure evolution and mechanical properties of the magnesium alloys is investigated.The TiC addition improves the interactions of laser with alloy powder and laser absorption rate of alloy powder,and decreases powder spatter of powder bed.The results show that high relative density of~99.4%and good surface roughness of~12μm are obtained for the LPBF-fabricated composites.The TiC addition promotes the precipitation of β-Mg_(17)Al_(12)in the alloys and the transformation of coarse columnar to fine equiaxed grains,where the grains are refined to~3.1μm.The TiC/AZ91D composites exhibit high microhardness of 114.6±2.5 HV_(0.2),high tensile strength of~345.0 MPa and a uniform elongation~4.1%.The improvement of tensile strength for the composites is ascribed to the combination of grain refinement strengthening and Orowan strengthening fromβ-Mg_(17)Al_(12)precipitates and Al_8Mn_5 nanoparticles.In the composites,the unmelted TiC particles can act as an anchor for the network structure of β-Mg_(17)Al_(12)precipitates,effectively impeding crack propagation and enhancing their performance.This work offers an insight to fabricating high-performance magnesium matrix composites by laser additive manufacturing.展开更多
Laser powder bed fusion(LPBF)of Mg alloys mainly focuses on the traditional commercial casting Mg alloys such as AZ91D,ZK60 and WE43,which usually display relatively low tensile strengths.Herein we developed a novel h...Laser powder bed fusion(LPBF)of Mg alloys mainly focuses on the traditional commercial casting Mg alloys such as AZ91D,ZK60 and WE43,which usually display relatively low tensile strengths.Herein we developed a novel high-strength Mg-12 Gd-2 Y-1 Zn-0.5 Mn(wt.%,GWZ1221M)alloy for the LPBF additive manufacturing process,and the evolution of microstructure and mechanical properties from the as-built state to LPBF-T4 and LPBF-T6 states was systematically investigated.The as-built GWZ1221M alloy exhibited fine equiaxed grains with an average grain size of only 4.3±2.2μm,while the as-cast alloy displayed typical coarse dendrite grains(178.2±73.6μm).Thus,the as-built alloy showed significantly higher tensile strengths than the as-cast counterpart,and its yield strength(YS),ultimate tensile strength(UTS)and elongation(EL)were 315±8 MPa,340±7 MPa and 2.7±0.5%respectively.Solution treatment transformed hard and brittleβ-(Mg,Zn)_(3)(Gd,Y)phase into basal X phase and lamellar long period stacking ordered(LPSO)with better plastic deformability,leading to the improvement of EL.Then peak-aging heat treatment introduced numerous nano-sized prismaticβprecipitates inside grains,resulting in the enhancement of YS.Finally,the LPBF-T6 alloy achieved appreciably high strength with YS,UTS and EL of 320±3 MPa,395±4 MPa and 2.1±0.4%respectively.Both as-built and LPBF-T6 GWZ1221M alloys showed remarkably higher tensile strengths than the as-cast counterparts and as-built commercial Mg alloys,highlighting the great potential of high-strength as-built Mg-Gd based alloys for structural applications.展开更多
基金National Key Research and Development Program of China(2023YFB4606400)Supported by Longmen Laboratory Frontier Exploration Topics(LMQYTSKT003)。
文摘Copper manufactured by laser powder bed fusion(LPBF)process typically exhibits poor strength-ductility coordination,and the addition of strengthening phases is an effective way to address this issue.To explore the effects of strengthening phases on Cu,Cu-carbon nanotubes(CNTs)composites were prepared using LPBF technique with Cu-CNTs mixed powder as the matrix.The formability,microstructure,mechanical properties,electrical conductivity,and thermal properties were studied.The result shows that the prepared composites have high relative density.The addition of CNTs results in inhomogeneous equiaxed grains at the edges of the molten pool and columnar grains at the center.Compared with pure copper,the overall mechanical properties of the composite are improved:tensile strength increases by 52.8%and elongation increases by 146.4%;the electrical and thermal properties are also enhanced:thermal conductivity increases by 10.8%and electrical conductivity increases by 12.7%.
基金supported by the Natural Science Foundation of Jiangsu Higher Education Institutions of China(Grant No.23KJD460003)the Scientific Research Foundation for High-level Talents of Nanjing Institute of Technology(Grant No.YKJ202103)the National Natural Science Foundation of China(Grant Nos.92463301,92163215,52205471,52305470).
文摘In this study,carbon nanotubes(CNTs)/AlSi10Mg composite parts with CNTs contents ranging from 0.0 to 2.0wt.%were successfully fabricated via laser powder bed fusion(LPBF)with laser scan speeds ranging from 900 to 1,900 mm·s^(-1).Uniform dispersion of CNTs in the powders can be achieved when their content is below 2.0wt.%.In the LPBF samples,the morphology of the CNTs is found to be directly related to their content.Especially,the length of CNTs in samples prepared by LPBF increases as the CNT content increases.The length of CNTs is approximately 200-300 nm in the 1.0wt.%CNTs/AlSi10Mg composites and approximately 500-1,000 nm in the 2.0wt.%CNTs/AlSi10Mg composites.The hardness of the composites reaches its highest value of 143.3 HV when the CNTs content is 1.0wt.%and the laser scan speed is 1,300 mm·s^(-1).It is found that the self-lubricating properties of the CNTs improve the tribological properties of the composites.The coefficient of friction(CoF)and wear rate of the samples decrease with increasing CNT content.At a CNTs content of 2.0wt.%,the CoF and wear rate of the composite decrease by approximately 14%and 30%,respectively,compared to the unreinforced matrix.The presence of CNTs leads to a more complete and refined network microstructure within the samples.Both the CNTs and the aluminum carbide contribute to the Orowan mechanism and the Hall-Petch effect within the matrix.
文摘激光粉末床熔融(Laser Powder Bed Fusion,LPBF)是金属增材制造技术中的重要分支,具有个性化、自动化等优势。然而,在逐层制造过程中由于残余应力不断积累,易引发变形、断裂、疲劳等问题,限制了其进一步应用。为预测金属增材制造件的位移和残余应力,借助开源有限元求解代码JAX-FEM,开展基于热弹塑性本构模型的LPBF全尺寸热-力耦合数值模拟研究。其中,根据能量守恒定律确定等效激光功率、等效激光半径及扫描速度,简化计算模型、减少计算时间;通过修改制件底面的应力状态实现模拟制件从基板上切割分离的过程,并预测了应力释放的影响。分析扫描策略与速度对LPBF热-力耦合行为的影响,对比发现,采用水平Z形扫描策略相较于垂直扫描策略所产生的最大位移降低了24.0%,最大残余应力降低了13.6%;当扫描速度从0.8m/s增大到1.6m/s时,产生的最大位移降低了6.4%,最大残余应力降低了5.2%。该研究有助于为调控LPBF残余应力和变形提供科学指导。
基金supported by the National Natural Science Foundation of China(Nos.52025053 and 52235006)the National Key R&D Program of China(No.2022YFB4600500).
文摘Superelastic NiTi alloys produced through laser powder bed fusion(LPBF)hold great promise in advancing wear-resistant transmission devices for aerospace and related applications.However,limited research on their wear behavior and strategies for enhancing wear resistance raises concerns about their future application prospects.In this study,a straightforward yet highly effective pre-strain treatment method is introduced,resulting in a nearly twofold improvement in the wear resistance of LPBF-fabricated NiTi alloys.This method prunes microstructure characteristics,influences the martensitic transformation process that improves cyclic compression superelasticity and transforms the distribution characteristics of adhesion stress acting on the indenter during wear processes,thereby effectively enhancing wear resistance.Additionally,the present study proposes an analytical model that establishes a link between superelastic metal cyclic compression characteristics and wear behaviors,providing insight into the wear characteristics,especially for adhesive wear patterns of superelastic metals including LPBF-fabricated NiTi alloys through analysis of cyclic compression curve.This research contributes to the fundamental understanding of wear resistance mechanisms in superelastic engineering materials and opens avenues for further optimization in related applications.
基金financially supported by the National Key Research and Development Program of China(2022YFB4602700)the National Natural Science Foundation of China(No.51975018)the Beijing Natural Science Foundation(No.2244085).
文摘Silicon-based anodes,utilizing nanosized silicon materials,hold great promise for the next-generation of lithium-ion batteries due to their high capacity and stable expansion.This study aims to address challenges in traditional slurry-coated anodes,such as agglomeration and low adhesive strength,through the application of laser powder bed fusion(LPBF).The process involves fabricating an Al-Si-Cu alloy layer on a Cu foil current collector,followed by dealloying to create a porous Si-Cu anode.Simulated and experimental results demonstrate successful alloy layer formation through optimized laser spot(55μm)and powder sizes(1-5μm).Controlled cooling produces primary Si particles ranging from 150 nm to 1μm.The resulting microstructure enhances electrochemical performance,particularly by tailoring the size of primary Si.The resultant porous Si-Cu anode,featuring uniformly distributed primary Si(200 nm)metallurgically bonded with Cu networks,exhibits an initial coulombic efficiency of 83% and a remarkable capacity retention of 80% after 300 cycles at 2 C.In-situ and ex-situ observations confirm the crucial role of anode architecture in performance enhancement.This study elucidates the influence of the LPBF microstructure on anode performance and broadens the potential application of laser powder bed fusion in battery manufacturing.
基金supported by National Natural Science Foundation of China(Grant Nos.52071299,51804280)Special Fund for Science and Technology Innovation Teams of Shanxi Province,China(Grant No.202304051001029)+3 种基金Major Science and Technology Projects of Shanxi Province,China(Grant Nos.20181101009,20201102009)Scientific and Technological Achievements Transformation Guidance Project of Shanxi Province,China(Grant No.202204021301048)Fundamental Research Program of Shanxi Province,China(Grant No.202203021212117)Young Elite Scientists Sponsorship Program by CAST(Grant No.2023QNRC001)。
文摘Based on the actual conditions of laser powder bed fusion(LPBF),a three-dimensional transient thermal-structural coupling single-layer finite element model was established to simulate the LPBF of Al-Cu-Mg-Si alloys.After characterizing the thermal behavior and residual stress distribution of the molten pool under different LPBF parameters,the cracking mechanisms of the Al-Cu-Mg-Si alloy were revealed.With an increase in the number of scanning tracks,the maximum cooling rate decreased gradually,whereas the maximum heating rate first increased and then decreased.The residual stress of the printed parts after cooling was primarily tensile stress.The residual stress along the scanning direction was mainly distributed in the center of the printing layer,whereas the residual stress perpendicular to the scanning direction was mainly concentrated in the center of the track.The residual stress along the deposition direction decreased with increasing distance from the substrate,with the highest stress occurring at the contact position with the substrate.Compared with the scanning speed,the laser power had a greater effect on the temperature and residual stress.The reliability of the numerical simulation was verified based on the size of the molten pool and the direction of crack propagation.
基金supported by the National Natural Science Foundation of China(Nos.52275333,52375335 and U22A202494)the Stabilization Support Project of AVIC Manufacturing Technology Institute(No.KZ571801)+1 种基金the Knowledge Innovation Special Project of Wuhan(No.2022010801010302)the Fundamental Research Funds for the Central Universities(No.YCJJ20230359).
文摘WE43 is a high-strength magnesium alloy containing rare-earth elements such as Y,Gd and Nd.Nevertheless,how to further obtain the balance of strength and ductility,as well as the manufacture of complex structures is still a dilemma for its engineering application.In this study,WE43 alloy samples withfine microstructures,high densification and excellent mechanical properties were successfully prepared by laser powder bed fusion(LPBF)additive manufacturing.The optimal process window was established,and the formation mechanisms of three types of porosity defects were revealed,namely lack-of-fusion pores,meltfluctuation-induced pores,and keyhole-induced pores.With the combined process of laser power of 200 W and scanning speed of 600 mm/s,samples with a high density of 99.89%were obtained.Furthermore,periodic heterogeneous microstructure was prepared along the build direction,i.e.,fine grains(∼4.1μm)at melt pool boundaries and coarse grain(∼23.6μm)inside melt pool.This was mainly due to the preferential precipitation of Zr and Mg_(3)(Gd,Nd)nano-precipitates at the melt pool boundaries providing nucleation sites for the grains.This special feature could provide an extra hetero-deformation induced(HDI)strengthening and retard fracture.The optimal tensile yield strength,ultimate tensile strength and elongation at break were 276±1 MPa,292±1 MPa and 6.1±0.2%,respectively.The obtained tensile properties were superior to those of other magnesium alloys and those fabricated by other processes.The solid solution strengthening(∼24.5%),grain boundary strengthening(∼14.4%)and HDI strengthening(∼32.2%)were the main sources of high yield strength.This work provides a guidance on studying the pore defect suppression and strengthening mechanisms of WE43 alloy and other magnesium alloys produced by LPBF.
基金supported by the National Key Research and Development Program of China (No.2021YFB3701000)the National Natural Science Foundation of China (Nos. U21A2047, 52201129, 51821001,U2037601)+1 种基金the support by the China Postdoctoral Science Foundation (No. 2023M742219)the Postdoctoral Fellowship Program (Grade B) of CPSF(No. GZB20240419)
文摘As a universal casting Mg-RE alloy,Mg-6Gd-3Y-Zr(GW63K,wt.%)alloy exhibits superior strength-ductility synergy and holds significant potential for engineering applications.In this study,the GW63K alloy is produced using the laser powder bed fusion(LPBF)additive manufacturing(AM)process for the first time.The printability,microstructure characteristics,and post-heat treatment conditions of the GW63K alloy are systematically investigated.The as-built GW63K samples demonstrate high relative densities exceeding 99.6%and exhibit no macroscopic and microscopic cracking across a wide range of process parameters,indicating excellent printability.An exceptional heterogeneous microstructure is observed in the as-built GW63K alloy,comprising coarse columnar grains,fine equiaxed grains with an average grain size of 21.72μm,uniformly distributed nano-sized Mg_(24)(Gd,Y)_(5)secondary phase,and numerous dislocations.Consequently,the as-built GW63K alloy displays enhanced tensile strengths and ductility compared to the as-cast alloy,with yield strength(YS),ultimate tensile strength(UTS)and elongation(EL)values of 218±4 MPa,284±5 MPa and 11.9±1.6%respectively.Additionally,due to the absence of coarse micron-sized secondary phase,a specific direct aging(T5)heat treatment regime at 200℃for 128 h is optimized for the as-built GW63K alloy to introduce dense and dispersedβ’aging precipitates.This T5 treatment surpasses the conventional solution plus aging(T6)heat treatment in enhancing mechanical properties.The LPBF-T5 GW63K alloy exhibits YS,UTS and EL values of 293±6 MPa,359±4 MPa and 2.9±0.7%,respectively.Notably,the YS of the LPBF-T5 alloy represents the highest value for the GW63K alloy,even surpassing that of the extrusion-T5 alloy.This study indicates that the GW63K alloy is a highly promising material for manufacturing near-net-shape high-strength Mg alloy components with intricate geometries using LPBF.
基金supported by the National Natural Science Foundation of China(Nos.52235008 and U2341270)the National Natural Science Foundation of China(No.52105341)。
文摘Poly-ether-ether-ketone/nano-silicon nitride(PEEK/nSN)composite scaffolds,fabricated by laser powder bed fusion(LPBF),show great potential for orthopedic applications due to their excellent biological performance and mechanical adaptability.However,the effect of nSN on LPBF processability and scaffold properties remains unclear.This study systematically investigates the processability and mechanical per-formance of PEEK/nSN composites to enable reliable clinical fabrication.The results show that adding nSN improves powder flowability and inhibits crystallization,enhancing LPBF processability.The introduction of nSN reduces PEEK’s non-isothermal crystallization Avrami exponent from 3.04 to 2.01,suggesting a transformation from a three-dimensional spherulitic to a two-dimensional lamellar crystal structure.Tensile tests reveal that the presence of nSN alters the optimal process parameters,reducing the optimal laser power from 25 W to 22 W due to increased energy absorption efficiency,as shown by an increase in absorbance at 843 cm^(-1)from 0.27 to 0.35 as the nSN content increases to 2 wt%.Porous diamond-structured scaffolds were fabricated using optimal parameters for pure PEEK,PEEK/1 wt%nSN,and PEEK/2 wt%nSN.Diamond-structured scaffolds fabricated with 1 wt%nSN showed a 12.2%increase in elastic modulus compared to pure PEEK,highlighting the enhanced mechanical performance.Over-all,this study offers key insights into the stable and customizable LPBF fabrication of PEEK/nSN porous scaffolds,providing a foundation for future research on their bioactivity and antibacterial properties for orthopedic applications.
基金supported by the National Natural Science Foundation of China(52205382,52225503)National Key Research and Development Program(2023YFB4603300)+1 种基金Key Research and Development Program of Jiangsu Province(BZ2024019,BE2022069)International Joint Laboratory of Sustainable Manufacturing,Ministry of Education and the Fundamental Research Funds for the Central Universities(NG2024014,XCA2300501)。
文摘The addition of ceramic reinforcements provides a promising approach to achieving high-performance magnesium matrix composites.In this work,AZ91D magnesium alloys and 2 wt.%TiC/AZ91D composites have been manufactured by laser powder bed fusion(LPBF)with variations of laser processing parameters.The effect of TiC reinforcement addition on the laser absorption behaviors,forming quality,microstructure evolution and mechanical properties of the magnesium alloys is investigated.The TiC addition improves the interactions of laser with alloy powder and laser absorption rate of alloy powder,and decreases powder spatter of powder bed.The results show that high relative density of~99.4%and good surface roughness of~12μm are obtained for the LPBF-fabricated composites.The TiC addition promotes the precipitation of β-Mg_(17)Al_(12)in the alloys and the transformation of coarse columnar to fine equiaxed grains,where the grains are refined to~3.1μm.The TiC/AZ91D composites exhibit high microhardness of 114.6±2.5 HV_(0.2),high tensile strength of~345.0 MPa and a uniform elongation~4.1%.The improvement of tensile strength for the composites is ascribed to the combination of grain refinement strengthening and Orowan strengthening fromβ-Mg_(17)Al_(12)precipitates and Al_8Mn_5 nanoparticles.In the composites,the unmelted TiC particles can act as an anchor for the network structure of β-Mg_(17)Al_(12)precipitates,effectively impeding crack propagation and enhancing their performance.This work offers an insight to fabricating high-performance magnesium matrix composites by laser additive manufacturing.
基金supported by the National Key Research and Development Program of China(No.2021YFB3701000)the National Natural Science Foundation of China(Nos.51971130,52201129,U21A2047,51821001,U2037601)。
文摘Laser powder bed fusion(LPBF)of Mg alloys mainly focuses on the traditional commercial casting Mg alloys such as AZ91D,ZK60 and WE43,which usually display relatively low tensile strengths.Herein we developed a novel high-strength Mg-12 Gd-2 Y-1 Zn-0.5 Mn(wt.%,GWZ1221M)alloy for the LPBF additive manufacturing process,and the evolution of microstructure and mechanical properties from the as-built state to LPBF-T4 and LPBF-T6 states was systematically investigated.The as-built GWZ1221M alloy exhibited fine equiaxed grains with an average grain size of only 4.3±2.2μm,while the as-cast alloy displayed typical coarse dendrite grains(178.2±73.6μm).Thus,the as-built alloy showed significantly higher tensile strengths than the as-cast counterpart,and its yield strength(YS),ultimate tensile strength(UTS)and elongation(EL)were 315±8 MPa,340±7 MPa and 2.7±0.5%respectively.Solution treatment transformed hard and brittleβ-(Mg,Zn)_(3)(Gd,Y)phase into basal X phase and lamellar long period stacking ordered(LPSO)with better plastic deformability,leading to the improvement of EL.Then peak-aging heat treatment introduced numerous nano-sized prismaticβprecipitates inside grains,resulting in the enhancement of YS.Finally,the LPBF-T6 alloy achieved appreciably high strength with YS,UTS and EL of 320±3 MPa,395±4 MPa and 2.1±0.4%respectively.Both as-built and LPBF-T6 GWZ1221M alloys showed remarkably higher tensile strengths than the as-cast counterparts and as-built commercial Mg alloys,highlighting the great potential of high-strength as-built Mg-Gd based alloys for structural applications.
