ZGH401 alloy was prepared under varying laser power levels and scanning speeds by the orthogonal test method using selective laser melting(SLM).The effect of different energy densities on microstructure and mechanical...ZGH401 alloy was prepared under varying laser power levels and scanning speeds by the orthogonal test method using selective laser melting(SLM).The effect of different energy densities on microstructure and mechanical properties of the formed alloy was investigated.The microstructure of ZGH401 was analyzed by scanning electron microscope,electron back-scattered diffraction,and electron probe microanalysis.The results show that the defects of the as-built ZGH401 are gradually reduced,the relative density is correspondingly enhanced with increasing the energy density,and the ultimate density can reach 99.6%.An increase in laser power leads to a corresponding rise in hardness of ZGH401,while a faster scanning speed reduces the residual stress in asbuilt ZGH401 samples.In addition,better tensile properties are achieved at room temperature due to more grain boundaries perpendicular to the build direction than parallel to the build direction.The precipitated phases are identified as carbides and Laves phases via chemical composition analysis,with fewer carbides observed at the molten pool boundaries than within the molten pools.展开更多
Additive manufacturing(AM)is an advanced production method for layer-by-layer fabrication,offering a paradigm shift in manufacturing.However,the sustainability of AM processes is poor,since suppliers recommend reusing...Additive manufacturing(AM)is an advanced production method for layer-by-layer fabrication,offering a paradigm shift in manufacturing.However,the sustainability of AM processes is poor,since suppliers recommend reusing 50%-70%of reprocessed powder,contributing to a significant increase in material disposal.To explore the possibility of fully reusing the polymeric material,we conduct a comprehensive characterisation of the powder particulates,in combination with analysis of the final prints.Utilizing optical and scanning electron microscopes,we statistically evaluate the size,morphology,and shape of the particles.Furthermore,tensile strength and deformation of printed bars is evaluated,showcasing the impact of aging on the print properties.The findings reveal that consecutive reuse of used powder significantly influences dimensional accuracy of the printed parts.We detect a 30.63%relative value of shrinkage after six printing iterations,which corresponds to an absolute shrinkage increase by 0.98%.This is significant considering the standard shrinkage for the material used is already 3.2%.Additionally,parts that are printed with reused material exhibit a small increase in elongation at yield,as well as an unexpected rise in tensile strength.Significant agglomeration of small particles is observed in the aged powder,since there are particles of less than 10μm,which are not found in the virgin powder.These results contribute to a better understanding of the issues related to the reusing of aged material,and offer invaluable insights for mitigating the environmental impact that is associated with material disposal in AM.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
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
Selective laser melting(SLM)plays a critical role in additive manufacturing,particularly in the fabrication of complex high-precision components.This study selects the AlSi10Mg alloy for its extensive use in the aeros...Selective laser melting(SLM)plays a critical role in additive manufacturing,particularly in the fabrication of complex high-precision components.This study selects the AlSi10Mg alloy for its extensive use in the aerospace and automotive industries,which require lightweight structures with superior thermal and mechanical properties.The thermal load induces residual tensile stress,leading to a decline in the geometric accuracy of the workpiece and causing cracks that reduce the fatigue life of the alloy.The rapid movement of the laser heat source during the material formation creates a localized and inhomogeneous temperature field in the powder bed.Significant temperature gradients are generated,resulting in thermal stresses and distortions within the part,affecting the quality of the molding.Therefore,understanding the effects of processing parameters and scanning strategies on the temperature field in SLM is crucial.To address these issues,this study proposes a multiscale method for predicting the complex transient temperature field during the manufacturing process based on the heat-conduction equation.Considering the influence of temperature on the material properties,a temperature-prediction model for discontinuous scanning paths in SLM and a temperature field-calculation model for irregular scanning paths are developed.The models are validated using finite-element results and are in excellent agreement.The analytical model is then used to investigate the effects of the laser power,scanning speed,and scanning spacing on the temperature distribution.The results reveal that the peak temperature decreases exponentially with increasing scanning speed and increases linearly with increasing laser power.In addition,with increasing scanning spacing,the peak temperature of the adjacent tracks near the observation point decreases linearly.These findings are critical for optimizing the SLM-process parameters and improving the material-forming quality.展开更多
Because of an unfortunate mistake during the production of this article,the Acknowledgements have been omitted.The Acknowledgements are added as follows:Sasan YAZDANI would like to thank the Scientific and Technologic...Because of an unfortunate mistake during the production of this article,the Acknowledgements have been omitted.The Acknowledgements are added as follows:Sasan YAZDANI would like to thank the Scientific and Technological Research Council of Turkey(TÜB˙ITAK)for receiving financial support for this work through the 2221 Fellowship Program for Visiting Scientists and Scientists on Sabbatical Leave(Grant ID:E 21514107-115.02-228864).Sasan YAZDANI also expresses his gratitude to Sahand University of Technology for granting him sabbatical leave to facilitate the completion of this research.展开更多
Selective laser melting(SLM)is a cost-effective 3 D metal additive manufacturing(AM)process.However,AM 316 L stainless steel(SS)has different surface and microstructure properties as compared to conventional ones.Bori...Selective laser melting(SLM)is a cost-effective 3 D metal additive manufacturing(AM)process.However,AM 316 L stainless steel(SS)has different surface and microstructure properties as compared to conventional ones.Boriding process is one of the ways to modify and increase the surface properties.The aim of this study is to predict and understand the growth kinetic of iron boride layers on AM 316 L SS.In this study,the growth kinetic mechanism was evaluated for AM 316 L SS.Pack boriding was applied at 850,900 and 950℃,each for 2,4 and 6 h.The thickness of the boride layers ranged from(1.8±0.3)μm to(27.7±2.2)μm.A diffusion model based on error function solutions in Fick’s second law was proposed to quantitatively predict and elucidate the growth rate of FeB and Fe_(2)B phase layers.The activation energy(Q)values for boron diffusion in FeB layer,Fe_(2)B layer,and dual FeB+Fe_(2)B layer were found to be 256.56,161.61 and 209.014 kJ/mol,respectively,which were higher than the conventional 316 L SS.The findings might provide and open new directions and approaches for applications of additively manufactured steels.展开更多
Selective laser melting,a predominant additive manufacturing technology for fabricating geometrically complex components,faces signifcant challenges when processing high-performance Ni-based superalloys containing ele...Selective laser melting,a predominant additive manufacturing technology for fabricating geometrically complex components,faces signifcant challenges when processing high-performance Ni-based superalloys containing elevated Al and Ti concentrations(typically>6 wt%),particularly regarding micro-cracking susceptibility.In this study,we demonstrate the successful fabrication of a novel crack-free Ni-based superalloy with 6.4 wt%(Al+Ti)content via optimized energy density,systematically investigating its microstructure,defects,and mechanical properties.Process parameter analysis revealed that insufcient energy densities led to unmolten pores,while excessively high energy densities caused keyhole formation.With an optimal energy density of 51.1 J/mm3,the crack-free superalloy exhibited exceptional mechanical properties:room temperature tensile strength of 1130 MPa with 36%elongation and elevated-temperature strength reaching 1198 MPa at 750℃.This strength enhancement correlates with the precipitation of nanoscaleγ′phases(mean size:31.56 nm)during high temperature.Furthermore,the mechanism of crack suppression is explained from multiple aspects,including energy density,grain structure,grain boundary characteristics,and the distribution of secondary phases.The absence of low-melting-point eutectic phases and brittle phases during the printing process is also explained from the perspective of alloy composition.These fndings provide a comprehensive framework for alloy design and process optimization in additive manufacturing of defect-resistant Ni-based superalloys.展开更多
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
In order to obtain high-density dual-scale ceramic particles(8.5 wt.%SiC+1.5 wt.%TiC)reinforced Al-Mg Sc-Zr composites with uniform microstructure,50 nm TiC and 7μm SiC particles were pre-dispersed into 15−53μm alum...In order to obtain high-density dual-scale ceramic particles(8.5 wt.%SiC+1.5 wt.%TiC)reinforced Al-Mg Sc-Zr composites with uniform microstructure,50 nm TiC and 7μm SiC particles were pre-dispersed into 15−53μm aluminum alloy powders by low-speed ball milling and mechanical mixing technology,respectively.Then,the effects of laser energy density,power and scanning rate on the density of the composites were investigated based on selective laser melting(SLM)technology.The effect of micron-sized SiC and nano-sized TiC particles on solidification structure,mechanical properties and fracture behaviors of the composites was revealed and analyzed in detail.Interfacial reaction and phase variations in the composites with varying reinforced particles were emphatically considered.Results showed that SiC-TiC particles could significantly improve forming quality and density of the SLMed composites,and the optimal relative density was up to 100%.In the process of laser melting,a strong chemical reaction occurs between SiC and aluminum matrix,and micron-scale acicular Al_(4)SiC_(4) bands were formed in situ.There was no interfacial reaction between TiC particles and aluminum matrix.TiC/Al semi-coherent interface had good bonding strength.Pinning effect of TiC particles in grain boundaries could prevent the equiaxial crystals from growing and transforming into columnar crystals,resulting in grain refinement.The optimal ultimate tensile strength(UTS),yield strength(YS),elongation(EL)and elastic modulus of the SiC-TiC/Al-Mg-Sc-Zr composite were~394 MPa,~262 MPa,~8.2%and~86 GPa,respectively.The fracture behavior of the composites included ductile fracture of Al matrix and brittle cleavage fracture of Al_(4)SiC_(4) phases.A large number of cross-distributed acicular Al_(4)SiC_(4) bands were the main factors leading to premature failure and fracture of SiC-TiC/Al-Mg-Sc-Zr composites.展开更多
In clinical settings,tantalum(Ta)is extensively implemented as a bone implant material.Ta is highly stable and biocompatible in vivo,being one of the metallic biomaterials having high affinity for bone tissue.However,...In clinical settings,tantalum(Ta)is extensively implemented as a bone implant material.Ta is highly stable and biocompatible in vivo,being one of the metallic biomaterials having high affinity for bone tissue.However,since Ta is a refractory metal,its application as bone implant material is limited.Most recently,additive manufacturing technology has introduced a novel approach to producing Ta implants.The present study compared the microstructure,surface and mechanical characteristics,and in vitro and in vivo biological characteristics of selective laser melted Ta(SLM Ta),selective laser melted titanium alloy Ti6Al4V with Ta coating(SLM Ti6Al4V with Ta coating),and selective laser melted Ti6Al4V(SLM Ti6Al4V).Results indicate that SLM Ta possesses superior mechanical characteristics contrasted with SLM Ti6Al4V and SLM Ti6Al4V with Ta coating.Furthermore,SLM Ta has anti-inflammatory activity,excellent osseointegration performance,and osteogenic bioactivity.We fabricated an SLM porous Ta bone plate and employed it for internal fixation of ulnar and radius fractures,which has been known to promote fracture healing.Further,the SLM porous Ta bone plate could form an integrated bone plate structure with the bone tissue at the implant site.Afterward,the porous structure of the plate minimizes its elastic modulus and eliminates stress shielding,leaving no need for further surgical removal.In conclusion,the SLM porous Ta bone plate meets the performance requirements(stimulating bone regeneration,non-stress shelter,and no need for second surgery)of an ideal bone plate and may revolutionize the field of internal fixation bone plates for fractures.展开更多
The corrosion resistance and antibacterial properties of Ti−3Cu alloy prepared by selective laser melting were evaluated using electrochemical experiments and a variety of antibacterial characterization.It is found th...The corrosion resistance and antibacterial properties of Ti−3Cu alloy prepared by selective laser melting were evaluated using electrochemical experiments and a variety of antibacterial characterization.It is found that the charge transfer resistance of Ti−3Cu alloy was 4.89×10^(5)Ω∙cm^(2),which was doubled the data obtained by CP-Ti alloy.The antibacterial rates of Ti−3Cu alloy against S.mutans and P.gingivalis were 45.0%and 54.5%.And the antibacterial rates increased with the prolongation of cultivation time,reaching up to 62.8%and 68.6%,respectively.The in-situ nano Ti_(2)Cu precipitates were homogeneously distributed in the matrix of the Ti−3Cu alloy,which was the key reason of increasing the corrosion resistance.Additionally,the microscale electric fields between theα-Ti matrix and the Ti_(2)Cu was responsible for the enhancement of the antibacterial properties.展开更多
Ti-Zr-Cu alloy has garnered signifcant attention in the feld of dental implants due to its excellent biocompatibility,antibacterial properties,and potentially controllable mechanical properties.However,two critical ch...Ti-Zr-Cu alloy has garnered signifcant attention in the feld of dental implants due to its excellent biocompatibility,antibacterial properties,and potentially controllable mechanical properties.However,two critical challenges remain in the selective laser melting(SLM)fabrication of Ti-Zr-Cu alloy:First,the high thermal conductivity of the Cu element tends to destabilize the solidifcation behavior of the molten pool,leading to uncontrollable pore defect evolution;Second,the infuence of process parameters on the synergistic efects of zirconium solution strengthening and copper precipitation strengthening is not well understood,hindering precise control over the material's mechanical properties.To address these issues,this study systematically elucidates the quantitative impact of energy input on the defect formation mechanisms and strengthening efects in the SLM processing of Ti15Zr5Cu alloy.By optimizing laser power(120–200 W)and scanning speed(450–1200 mm/s)through a full-factor experimental design,we comprehensively analyze the efects of energy input on defect morphology,microstructure evolution,and mechanical performance.The results demonstrate that as energy density decreases,defect types transition from spherical pores to irregular pores,signifcantly infuencing mechanical properties.Based on the defect evolution trends,three distinct energy density regions are identifed:the high-energy region,the lowenergy region,and the transition region.Under the optimal processing conditions of a laser power of 180 W and a scanning speed of 1200 mm/s,the Ti15Zr5Cu alloy exhibits a relative density of 99.998%,a tensile strength of 1490±11 MPa,and an elongation at break of 6.0%±0.5%.These properties ensure that the material satisfes the stringent requirements for high strength in narrow-diameter implants used in the maxilloanterior region.This study provides theoretical and experimental support for the process-property optimization of Ti-Zr-Cu alloys in additive manufacturing and promotes their application in the fabrication of high-performance,antibacterial dental implants.展开更多
Strong and ductile Al alloys and their suitable design strategy have long been desired in selective laser melting(SLM).This work reports a non-equilibrium partitioning model and a correspondingly designed Al–7.5Mg–0...Strong and ductile Al alloys and their suitable design strategy have long been desired in selective laser melting(SLM).This work reports a non-equilibrium partitioning model and a correspondingly designed Al–7.5Mg–0.5Sc–0.3Zr–0.6Si alloy.This model effectively quantifies the influence of Mg and Si on hot cracking in aluminum alloy by considering the non-equilibrium partitioning under high cooling rates in SLM.The designed Al–7.5Mg–0.5Sc–0.3Zr–0.6Si alloy exhibits no hot cracks and achieves a remarkably enhanced strength–ductility synergy(a yield strength of(412±8)MPa and a uniform elongation of(15.6±0.6)%),superior to previously reported Al–Mg–Sc–Zr and Al–Mn alloys.A tensile cracking model is proposed to explore the origin of the improved ductility.Both the non-equilibrium partitioning model and the novel Al–7.5Mg–0.5Sc–0.3Zr–0.6Si alloy offers a promising opportunity for producing highly reliable aluminum parts through SLM.展开更多
Al−3.51Mg−0.42Mn−0.76Sc−0.40Zr(wt.%)alloy was prepared by selective laser melting(SLM)method.The mechanical properties and microstructure of the alloy after annealing at 300℃or 325℃for 6 h were studied.The tensile s...Al−3.51Mg−0.42Mn−0.76Sc−0.40Zr(wt.%)alloy was prepared by selective laser melting(SLM)method.The mechanical properties and microstructure of the alloy after annealing at 300℃or 325℃for 6 h were studied.The tensile strength,yield strength and elongation of the SLM alloy were 339 MPa,213 MPa and 24%,respectively.After annealing at 300℃for 6 h,the tensile and yield strength of the alloy were increased to 518 MPa and 505 MPa,respectively,and the elongation decreased to 13%.After annealing at 325℃for 6 h,the yield strength of the alloy was reduced to 483 MPa.The grain size of the alloy after annealing at 300℃and 325℃did not grow significantly,but the segregation of Mg element was significantly reduced.Nanoscale Al3(Sc,Zr)phase was precipitated from the alloy matrix,and its average size increased with the increase of annealing temperature.Therefore,the strength improvement of the annealed SLM aluminum alloy was mainly attributed to the precipitation strengthening of Al3(Sc,Zr),and the strengthening mechanism was mainly dislocation cutting mechanism.When the annealing temperature was too high,the coarsening of Al3(Sc,Zr)particles caused the strength to decrease.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
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
The precise design and fabrication of biomaterial scaffolds is necessary to provide a systematic study for bone tissue engineering. Biomaterial scaffolds should have sufficient stiffness and large porosity. These two ...The precise design and fabrication of biomaterial scaffolds is necessary to provide a systematic study for bone tissue engineering. Biomaterial scaffolds should have sufficient stiffness and large porosity. These two goals generally contradict since larger porosity results in lower mechanical properties. To seek the microstructure of maximum stiffness with the constraint of volume fraction by topology optimization method, algorithms and programs were built to obtain 2D and 3D optimized microstructure and then they were transferred to CAD models of STL format. Ti scaffolds with 30% volume fraction were fabricated using a selective laser melting （SLM） technology. The architecture and pore shape in the metallic biomaterial scaffolds were relatively precise reproduced and the minimum mean pore size was 231μm. The accurate fabrication of intricate microstructure has verified that the SLM process is suitable for fabrication of metallic biomaterial scaffolds.展开更多
Selective laser melting(SLM)is an emerging layer-wise additive manufacturing technique that can generate complex components with high performance.Particulate-reinforced aluminum matrix composites(PAMCs)are important m...Selective laser melting(SLM)is an emerging layer-wise additive manufacturing technique that can generate complex components with high performance.Particulate-reinforced aluminum matrix composites(PAMCs)are important materials for various applications due to the combined properties of Al matrix and reinforcements.Considering the advantages of SLM technology and PAMCs,the novel SLM PAMCs have been developed and researched in recent years.Therefore,the current research progress about the SLM PAMCs is reviewed.Firstly,special attention is paid to the solidification behavior of SLM PAMCs.Secondly,the important issues about the design and fabrication of high-performance SLM PAMCs,including the selection of reinforcement,the influence of parameters on the processing and microstructure,the defect evolution and phase control,are highlighted and discussed comprehensively.Thirdly,the performance and strengthening mechanism of SLM PAMCs are systematically figured out.Finally,future directions are pointed out on the advancement of high-performance SLM PAMCs.展开更多
Defect formation is a common problem in selective laser melting （SLM）. This paper provides a review of defect formation mechanisms in SLM. It sum- marizes the recent research outcomes on defect findings and classifi...Defect formation is a common problem in selective laser melting （SLM）. This paper provides a review of defect formation mechanisms in SLM. It sum- marizes the recent research outcomes on defect findings and classification, analyzes formation mechanisms of the common defects, such as porosities, incomplete fusion holes, and cracks. The paper discusses the effect of the process parameters on defect formation and the impact of defect formation on the mechanical properties of a fabri- cated part. Based on the discussion, the paper proposes strategies for defect suppression and control in SLM.展开更多
基金National Defense Science and Technology Project Management Center(2021-JCJQ-JJ-0092)。
文摘ZGH401 alloy was prepared under varying laser power levels and scanning speeds by the orthogonal test method using selective laser melting(SLM).The effect of different energy densities on microstructure and mechanical properties of the formed alloy was investigated.The microstructure of ZGH401 was analyzed by scanning electron microscope,electron back-scattered diffraction,and electron probe microanalysis.The results show that the defects of the as-built ZGH401 are gradually reduced,the relative density is correspondingly enhanced with increasing the energy density,and the ultimate density can reach 99.6%.An increase in laser power leads to a corresponding rise in hardness of ZGH401,while a faster scanning speed reduces the residual stress in asbuilt ZGH401 samples.In addition,better tensile properties are achieved at room temperature due to more grain boundaries perpendicular to the build direction than parallel to the build direction.The precipitated phases are identified as carbides and Laves phases via chemical composition analysis,with fewer carbides observed at the molten pool boundaries than within the molten pools.
文摘Additive manufacturing(AM)is an advanced production method for layer-by-layer fabrication,offering a paradigm shift in manufacturing.However,the sustainability of AM processes is poor,since suppliers recommend reusing 50%-70%of reprocessed powder,contributing to a significant increase in material disposal.To explore the possibility of fully reusing the polymeric material,we conduct a comprehensive characterisation of the powder particulates,in combination with analysis of the final prints.Utilizing optical and scanning electron microscopes,we statistically evaluate the size,morphology,and shape of the particles.Furthermore,tensile strength and deformation of printed bars is evaluated,showcasing the impact of aging on the print properties.The findings reveal that consecutive reuse of used powder significantly influences dimensional accuracy of the printed parts.We detect a 30.63%relative value of shrinkage after six printing iterations,which corresponds to an absolute shrinkage increase by 0.98%.This is significant considering the standard shrinkage for the material used is already 3.2%.Additionally,parts that are printed with reused material exhibit a small increase in elongation at yield,as well as an unexpected rise in tensile strength.Significant agglomeration of small particles is observed in the aged powder,since there are particles of less than 10μm,which are not found in the virgin powder.These results contribute to a better understanding of the issues related to the reusing of aged material,and offer invaluable insights for mitigating the environmental impact that is associated with material disposal in AM.
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.
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supported by National Natural Science Foundation of the China Youth Program(Grant No.52205485)Sichuan Youth Fund Program of China(Grant No.2025ZNSFSC1275)the Young Scientific Research Team Cultivation Program of SUES(Grant No.QNTD202112)。
文摘Selective laser melting(SLM)plays a critical role in additive manufacturing,particularly in the fabrication of complex high-precision components.This study selects the AlSi10Mg alloy for its extensive use in the aerospace and automotive industries,which require lightweight structures with superior thermal and mechanical properties.The thermal load induces residual tensile stress,leading to a decline in the geometric accuracy of the workpiece and causing cracks that reduce the fatigue life of the alloy.The rapid movement of the laser heat source during the material formation creates a localized and inhomogeneous temperature field in the powder bed.Significant temperature gradients are generated,resulting in thermal stresses and distortions within the part,affecting the quality of the molding.Therefore,understanding the effects of processing parameters and scanning strategies on the temperature field in SLM is crucial.To address these issues,this study proposes a multiscale method for predicting the complex transient temperature field during the manufacturing process based on the heat-conduction equation.Considering the influence of temperature on the material properties,a temperature-prediction model for discontinuous scanning paths in SLM and a temperature field-calculation model for irregular scanning paths are developed.The models are validated using finite-element results and are in excellent agreement.The analytical model is then used to investigate the effects of the laser power,scanning speed,and scanning spacing on the temperature distribution.The results reveal that the peak temperature decreases exponentially with increasing scanning speed and increases linearly with increasing laser power.In addition,with increasing scanning spacing,the peak temperature of the adjacent tracks near the observation point decreases linearly.These findings are critical for optimizing the SLM-process parameters and improving the material-forming quality.
文摘Because of an unfortunate mistake during the production of this article,the Acknowledgements have been omitted.The Acknowledgements are added as follows:Sasan YAZDANI would like to thank the Scientific and Technological Research Council of Turkey(TÜB˙ITAK)for receiving financial support for this work through the 2221 Fellowship Program for Visiting Scientists and Scientists on Sabbatical Leave(Grant ID:E 21514107-115.02-228864).Sasan YAZDANI also expresses his gratitude to Sahand University of Technology for granting him sabbatical leave to facilitate the completion of this research.
文摘Selective laser melting(SLM)is a cost-effective 3 D metal additive manufacturing(AM)process.However,AM 316 L stainless steel(SS)has different surface and microstructure properties as compared to conventional ones.Boriding process is one of the ways to modify and increase the surface properties.The aim of this study is to predict and understand the growth kinetic of iron boride layers on AM 316 L SS.In this study,the growth kinetic mechanism was evaluated for AM 316 L SS.Pack boriding was applied at 850,900 and 950℃,each for 2,4 and 6 h.The thickness of the boride layers ranged from(1.8±0.3)μm to(27.7±2.2)μm.A diffusion model based on error function solutions in Fick’s second law was proposed to quantitatively predict and elucidate the growth rate of FeB and Fe_(2)B phase layers.The activation energy(Q)values for boron diffusion in FeB layer,Fe_(2)B layer,and dual FeB+Fe_(2)B layer were found to be 256.56,161.61 and 209.014 kJ/mol,respectively,which were higher than the conventional 316 L SS.The findings might provide and open new directions and approaches for applications of additively manufactured steels.
基金supported by the National Natural Science Foundation of China(Nos.51775140 and 52232004)supported by the Shenzhen Science and Technology Plan(KJZD20230923113900001).
文摘Selective laser melting,a predominant additive manufacturing technology for fabricating geometrically complex components,faces signifcant challenges when processing high-performance Ni-based superalloys containing elevated Al and Ti concentrations(typically>6 wt%),particularly regarding micro-cracking susceptibility.In this study,we demonstrate the successful fabrication of a novel crack-free Ni-based superalloy with 6.4 wt%(Al+Ti)content via optimized energy density,systematically investigating its microstructure,defects,and mechanical properties.Process parameter analysis revealed that insufcient energy densities led to unmolten pores,while excessively high energy densities caused keyhole formation.With an optimal energy density of 51.1 J/mm3,the crack-free superalloy exhibited exceptional mechanical properties:room temperature tensile strength of 1130 MPa with 36%elongation and elevated-temperature strength reaching 1198 MPa at 750℃.This strength enhancement correlates with the precipitation of nanoscaleγ′phases(mean size:31.56 nm)during high temperature.Furthermore,the mechanism of crack suppression is explained from multiple aspects,including energy density,grain structure,grain boundary characteristics,and the distribution of secondary phases.The absence of low-melting-point eutectic phases and brittle phases during the printing process is also explained from the perspective of alloy composition.These fndings provide a comprehensive framework for alloy design and process optimization in additive manufacturing of defect-resistant Ni-based superalloys.
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Project(2022J318)supported by the Natural Science Foundation of Ningbo,ChinaProject(2021A1515110525)supported by the Guangdong Basic and Applied Basic Research Foundation,ChinaProject(2022QN05023)supported by the Inner Mongolia Natural Science Foundation Youth Project,China。
文摘In order to obtain high-density dual-scale ceramic particles(8.5 wt.%SiC+1.5 wt.%TiC)reinforced Al-Mg Sc-Zr composites with uniform microstructure,50 nm TiC and 7μm SiC particles were pre-dispersed into 15−53μm aluminum alloy powders by low-speed ball milling and mechanical mixing technology,respectively.Then,the effects of laser energy density,power and scanning rate on the density of the composites were investigated based on selective laser melting(SLM)technology.The effect of micron-sized SiC and nano-sized TiC particles on solidification structure,mechanical properties and fracture behaviors of the composites was revealed and analyzed in detail.Interfacial reaction and phase variations in the composites with varying reinforced particles were emphatically considered.Results showed that SiC-TiC particles could significantly improve forming quality and density of the SLMed composites,and the optimal relative density was up to 100%.In the process of laser melting,a strong chemical reaction occurs between SiC and aluminum matrix,and micron-scale acicular Al_(4)SiC_(4) bands were formed in situ.There was no interfacial reaction between TiC particles and aluminum matrix.TiC/Al semi-coherent interface had good bonding strength.Pinning effect of TiC particles in grain boundaries could prevent the equiaxial crystals from growing and transforming into columnar crystals,resulting in grain refinement.The optimal ultimate tensile strength(UTS),yield strength(YS),elongation(EL)and elastic modulus of the SiC-TiC/Al-Mg-Sc-Zr composite were~394 MPa,~262 MPa,~8.2%and~86 GPa,respectively.The fracture behavior of the composites included ductile fracture of Al matrix and brittle cleavage fracture of Al_(4)SiC_(4) phases.A large number of cross-distributed acicular Al_(4)SiC_(4) bands were the main factors leading to premature failure and fracture of SiC-TiC/Al-Mg-Sc-Zr composites.
基金supported by the National Natural Science Foundation of China(No.82172398)Liaoning Revitalization Talents Program(No.XLYC2203102).
文摘In clinical settings,tantalum(Ta)is extensively implemented as a bone implant material.Ta is highly stable and biocompatible in vivo,being one of the metallic biomaterials having high affinity for bone tissue.However,since Ta is a refractory metal,its application as bone implant material is limited.Most recently,additive manufacturing technology has introduced a novel approach to producing Ta implants.The present study compared the microstructure,surface and mechanical characteristics,and in vitro and in vivo biological characteristics of selective laser melted Ta(SLM Ta),selective laser melted titanium alloy Ti6Al4V with Ta coating(SLM Ti6Al4V with Ta coating),and selective laser melted Ti6Al4V(SLM Ti6Al4V).Results indicate that SLM Ta possesses superior mechanical characteristics contrasted with SLM Ti6Al4V and SLM Ti6Al4V with Ta coating.Furthermore,SLM Ta has anti-inflammatory activity,excellent osseointegration performance,and osteogenic bioactivity.We fabricated an SLM porous Ta bone plate and employed it for internal fixation of ulnar and radius fractures,which has been known to promote fracture healing.Further,the SLM porous Ta bone plate could form an integrated bone plate structure with the bone tissue at the implant site.Afterward,the porous structure of the plate minimizes its elastic modulus and eliminates stress shielding,leaving no need for further surgical removal.In conclusion,the SLM porous Ta bone plate meets the performance requirements(stimulating bone regeneration,non-stress shelter,and no need for second surgery)of an ideal bone plate and may revolutionize the field of internal fixation bone plates for fractures.
基金financially supported by the National Natural Science Foundation of China(No.51404302)the Natural Science Foundation of Hunan Province,China(Nos.2020JJ4732,2022JJ30897)the Natural Science Foundation of Changsha City,China(No.kq2202430).
文摘The corrosion resistance and antibacterial properties of Ti−3Cu alloy prepared by selective laser melting were evaluated using electrochemical experiments and a variety of antibacterial characterization.It is found that the charge transfer resistance of Ti−3Cu alloy was 4.89×10^(5)Ω∙cm^(2),which was doubled the data obtained by CP-Ti alloy.The antibacterial rates of Ti−3Cu alloy against S.mutans and P.gingivalis were 45.0%and 54.5%.And the antibacterial rates increased with the prolongation of cultivation time,reaching up to 62.8%and 68.6%,respectively.The in-situ nano Ti_(2)Cu precipitates were homogeneously distributed in the matrix of the Ti−3Cu alloy,which was the key reason of increasing the corrosion resistance.Additionally,the microscale electric fields between theα-Ti matrix and the Ti_(2)Cu was responsible for the enhancement of the antibacterial properties.
基金supported by the National Natural Science Foundation of China(Nos.52401178 and U24A20713)the IMR Innovation Fund(No.2024-PY06)the CAS-WEGO Research and Development Plan Project.
文摘Ti-Zr-Cu alloy has garnered signifcant attention in the feld of dental implants due to its excellent biocompatibility,antibacterial properties,and potentially controllable mechanical properties.However,two critical challenges remain in the selective laser melting(SLM)fabrication of Ti-Zr-Cu alloy:First,the high thermal conductivity of the Cu element tends to destabilize the solidifcation behavior of the molten pool,leading to uncontrollable pore defect evolution;Second,the infuence of process parameters on the synergistic efects of zirconium solution strengthening and copper precipitation strengthening is not well understood,hindering precise control over the material's mechanical properties.To address these issues,this study systematically elucidates the quantitative impact of energy input on the defect formation mechanisms and strengthening efects in the SLM processing of Ti15Zr5Cu alloy.By optimizing laser power(120–200 W)and scanning speed(450–1200 mm/s)through a full-factor experimental design,we comprehensively analyze the efects of energy input on defect morphology,microstructure evolution,and mechanical performance.The results demonstrate that as energy density decreases,defect types transition from spherical pores to irregular pores,signifcantly infuencing mechanical properties.Based on the defect evolution trends,three distinct energy density regions are identifed:the high-energy region,the lowenergy region,and the transition region.Under the optimal processing conditions of a laser power of 180 W and a scanning speed of 1200 mm/s,the Ti15Zr5Cu alloy exhibits a relative density of 99.998%,a tensile strength of 1490±11 MPa,and an elongation at break of 6.0%±0.5%.These properties ensure that the material satisfes the stringent requirements for high strength in narrow-diameter implants used in the maxilloanterior region.This study provides theoretical and experimental support for the process-property optimization of Ti-Zr-Cu alloys in additive manufacturing and promotes their application in the fabrication of high-performance,antibacterial dental implants.
基金financially supported by the National Natural Science Foundation of China(No.52071321)the Science Foundation of Anhui,China(No.2108085QE189)+2 种基金the Major Research Development Program of Wuhu,China(Nos.2023yf107 and 2023yf063)the Major Projects of Anhui Provincial Department of Education,China(Nos.2022AH050956 and 2022AH050974)the Start-up funding of Anhui Polytechnic University,China(No.2022YQQ006)。
文摘Strong and ductile Al alloys and their suitable design strategy have long been desired in selective laser melting(SLM).This work reports a non-equilibrium partitioning model and a correspondingly designed Al–7.5Mg–0.5Sc–0.3Zr–0.6Si alloy.This model effectively quantifies the influence of Mg and Si on hot cracking in aluminum alloy by considering the non-equilibrium partitioning under high cooling rates in SLM.The designed Al–7.5Mg–0.5Sc–0.3Zr–0.6Si alloy exhibits no hot cracks and achieves a remarkably enhanced strength–ductility synergy(a yield strength of(412±8)MPa and a uniform elongation of(15.6±0.6)%),superior to previously reported Al–Mg–Sc–Zr and Al–Mn alloys.A tensile cracking model is proposed to explore the origin of the improved ductility.Both the non-equilibrium partitioning model and the novel Al–7.5Mg–0.5Sc–0.3Zr–0.6Si alloy offers a promising opportunity for producing highly reliable aluminum parts through SLM.
基金financially supported by the National Key Research and Development Program of China(No.2018YFB2001801)State’s Key Project of Research and Development Plan(No.2021YFC1910505)the Key Research and Development Program of Guangdong Province,China(No.2020B010186002)。
文摘Al−3.51Mg−0.42Mn−0.76Sc−0.40Zr(wt.%)alloy was prepared by selective laser melting(SLM)method.The mechanical properties and microstructure of the alloy after annealing at 300℃or 325℃for 6 h were studied.The tensile strength,yield strength and elongation of the SLM alloy were 339 MPa,213 MPa and 24%,respectively.After annealing at 300℃for 6 h,the tensile and yield strength of the alloy were increased to 518 MPa and 505 MPa,respectively,and the elongation decreased to 13%.After annealing at 325℃for 6 h,the yield strength of the alloy was reduced to 483 MPa.The grain size of the alloy after annealing at 300℃and 325℃did not grow significantly,but the segregation of Mg element was significantly reduced.Nanoscale Al3(Sc,Zr)phase was precipitated from the alloy matrix,and its average size increased with the increase of annealing temperature.Therefore,the strength improvement of the annealed SLM aluminum alloy was mainly attributed to the precipitation strengthening of Al3(Sc,Zr),and the strengthening mechanism was mainly dislocation cutting mechanism.When the annealing temperature was too high,the coarsening of Al3(Sc,Zr)particles caused the strength to decrease.
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 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Project (51275179) supported by the National Natural Science Foundation of ChinaProject (2010A090200072) supported by Industry,University and Research Institute Combination of Ministry of Education, Ministry of Science and Technology and Guangdong Province,China+1 种基金Project (2012M511797) supported by China Postdoctoral Science FoundationProject (2012ZB0014) supported by FundamentalResearch Funds for the Central Universities of China
文摘The precise design and fabrication of biomaterial scaffolds is necessary to provide a systematic study for bone tissue engineering. Biomaterial scaffolds should have sufficient stiffness and large porosity. These two goals generally contradict since larger porosity results in lower mechanical properties. To seek the microstructure of maximum stiffness with the constraint of volume fraction by topology optimization method, algorithms and programs were built to obtain 2D and 3D optimized microstructure and then they were transferred to CAD models of STL format. Ti scaffolds with 30% volume fraction were fabricated using a selective laser melting （SLM） technology. The architecture and pore shape in the metallic biomaterial scaffolds were relatively precise reproduced and the minimum mean pore size was 231μm. The accurate fabrication of intricate microstructure has verified that the SLM process is suitable for fabrication of metallic biomaterial scaffolds.
基金Project(GJHZ20190822095418365)supported by Shenzhen International Cooperation Research,ChinaProject(2019011)supported by NTUT-SZU Joint Research Program,China+2 种基金Project(2019040)supported by Natural Science Foundation of Shenzhen University,ChinaProject(JCYJ20190808144009478)supported by Shenzhen Fundamental Research Fund,ChinaProject(ZDYBH201900000008)supported by Shenzhen Bureau of Industry and Information Technology,China。
文摘Selective laser melting(SLM)is an emerging layer-wise additive manufacturing technique that can generate complex components with high performance.Particulate-reinforced aluminum matrix composites(PAMCs)are important materials for various applications due to the combined properties of Al matrix and reinforcements.Considering the advantages of SLM technology and PAMCs,the novel SLM PAMCs have been developed and researched in recent years.Therefore,the current research progress about the SLM PAMCs is reviewed.Firstly,special attention is paid to the solidification behavior of SLM PAMCs.Secondly,the important issues about the design and fabrication of high-performance SLM PAMCs,including the selection of reinforcement,the influence of parameters on the processing and microstructure,the defect evolution and phase control,are highlighted and discussed comprehensively.Thirdly,the performance and strengthening mechanism of SLM PAMCs are systematically figured out.Finally,future directions are pointed out on the advancement of high-performance SLM PAMCs.
基金Supported by National Natural Science Foundation of China(Grant No.51605077)Science Challenge Project(Grant No.CKY2016212A506-0101)Science Fund for Creative Research Groups of NSFC(Grant No.51621064)
文摘Defect formation is a common problem in selective laser melting （SLM）. This paper provides a review of defect formation mechanisms in SLM. It sum- marizes the recent research outcomes on defect findings and classification, analyzes formation mechanisms of the common defects, such as porosities, incomplete fusion holes, and cracks. The paper discusses the effect of the process parameters on defect formation and the impact of defect formation on the mechanical properties of a fabri- cated part. Based on the discussion, the paper proposes strategies for defect suppression and control in SLM.
