To explore the formation mechanism of anisotropy in Ti-6Al-4V alloy fabricated by selective laser melting(SLM),the compressive mechanical properties,microhardness,microstructure,and crystallographic orientation of the...To explore the formation mechanism of anisotropy in Ti-6Al-4V alloy fabricated by selective laser melting(SLM),the compressive mechanical properties,microhardness,microstructure,and crystallographic orientation of the alloy across different planes were investigated.The anisotropy of SLM-fabricated Ti-6Al-4V alloys was analyzed,and the electron backscatter diffraction technique was used to investigate the influence of different grain types and orientations on the stress-strain distribution at various scales.Results reveal that in room-temperature compression tests at a strain rate of 10^(-3) s^(-1),both the compressive yield strength and microhardness vary along the deposition direction,indicating a certain degree of mechanical property anisotropy.The alloy exhibits a columnar microstructure;along the deposition direction,the grains appear equiaxed,and they have internal hexagonal close-packed(hcp)α/α'martensitic structure.α'phase has a preferential orientation approximately along the<0001>direction.Anisotropy arises from the high aspect ratio of columnar grains,along with the weak texture of the microstructure and low symmetry of the hcp crystal structure.展开更多
Selective laser melting(SLM),as an additive manufacturing technology,has garnered widespread attention for its capability to fabricate components with complex geometries and to tailor the microstructure and mechanical...Selective laser melting(SLM),as an additive manufacturing technology,has garnered widespread attention for its capability to fabricate components with complex geometries and to tailor the microstructure and mechanical properties under specific conditions.However,the intrinsic influence mechanism of microstructure formation under non-equilibrium solidification conditions in SLM processes has not been clearly revealed.In the present work,the influence of Al concentration and process parameters on the microstructure forming mechanism of Al_(x)CoCrFeNi HEAs prepared by SLM is investigated by molecular dynamics simulation method.The simulation results show that the difference in Al content significantly affects the microstructure formation of HEAs,including the growth rate and morphology of columnar crystals,stress distribution at grain boundaries,and defect structure.In addition,the results show that increasing the substrate temperature improves the solidification formability,reduces microstructural defects,and helps reduce residual stress in Al_(x)CoCrFeNi HEAs.By analyzing the influence of heat and solute flow in the molten pool on the growth of columnar crystals,it is found that spatial fluctuations in Al concentration during the non-equilibrium solidification process inhibit the high cooling rates induced by steep temperature gradients.These findings promote the understanding of the forming mechanism of microstructure in HEAs prepared by SLM and provide theoretical guidance for designing high-performance SLM-fabricated HEAs.展开更多
350 keV He^(+) ions were injected into laser powder bed fusion(LPBF)-processed 304L stainless steel and traditional rolled 304L stainless steel with a flux of 1×10^(17) ions/cm^(2) at room temperature,followed by...350 keV He^(+) ions were injected into laser powder bed fusion(LPBF)-processed 304L stainless steel and traditional rolled 304L stainless steel with a flux of 1×10^(17) ions/cm^(2) at room temperature,followed by annealing at 750℃ for 10,100,and 300 h,respectively.The results showed that material swelling due to helium bubble coarsening was almost not observed in either the LPBF or rolled samples after 10 h of annealing duration.Rapid coarsening and swelling of bubbles occurred in the rolled samples,but only moderate bubble growth occurred in the LPBF sample after annealing for 100 h.After annealing for 300 h,the helium bubbles in both samples tended to grow steadily.For 10 h of annealing,the irradiated samples were in a disequilibrium state,and the apparent activation energy(E^(act))calculated by the Arrhenius model determined that helium atoms tended to diffuse through the displacement mechanism,and helium bubbles grew under the migration and coalescence(MC)mechanism.With annealing times over 100 h,the high-density dislocations and nano-oxide particles in the LPBF sample still had a strong trapping effect on the movement and growth of helium bubbles.After annealing for 300 h,the cellular subgrains in the LPBF sample decomposed,and the nano-oxide particles had no trapping effect on the helium bubbles.At this time,the dislocation structure played a primary role in suppressing the growth of helium bubbles,and the radiation resistance of the LPBF sample remained superior to that of the rolled samples.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
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
Austenitic stainless steel(ASS)is a common material used in high-pressure hydrogen systems.Prolonged exposure to high-pressure hydrogen can cause hydrogen embrittlement(HE),raising significant safety concerns.Selectiv...Austenitic stainless steel(ASS)is a common material used in high-pressure hydrogen systems.Prolonged exposure to high-pressure hydrogen can cause hydrogen embrittlement(HE),raising significant safety concerns.Selective Laser Melting(SLM),known for its high precision,is a promising additive manufacturing technology that has been widely adopted across various industries.Studies have reported that under certain SLM manufacturing conditions and process parameters,the HE resistance of SLM ASS is significantly better than that of conventionally manufactured(CM)ASS,showing great potential for application in high-pressure hydrogen systems.Thus,studying the HE of SLM ASS is crucial for further improving the safety of high-pressure hydrogen systems.This paper provides an overview of the SLM process,reviews the mechanisms of HE and their synergistic effects,and analyzes the HE characteristics of SLM ASS.Additionally,it examines the influence of unique microstructures and SLM process variables on HE of SLM ASS and offers recommendations for future research to enhance the safety of high-pressure hydrogen systems.展开更多
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
The effects of the Laves-decorated dendrite structure on the hydrogen-assisted cracking behavior of the SLM-718 alloy were investigated.The Laves phase exhibits a hydrogen desorption activation energy of 47.67±7....The effects of the Laves-decorated dendrite structure on the hydrogen-assisted cracking behavior of the SLM-718 alloy were investigated.The Laves phase exhibits a hydrogen desorption activation energy of 47.67±7.85 kJ mol^(-1).The results of in situ scanning Kelvin probe force microscopy and hydrogen microprint technique provide direct evidence of the hydrogen trapping by the Laves phase.The high-density dendrite walls consisting of entangled dislocations exhibit an inhibitory effect on hydrogen diffusion.Atomic-scale characterization reveals that dislocation stacking at the Laves/γ-matrix interface induces the formation of dislocation defects and a high-stress concentration in the Laves phase.The presence of hydrogen further promotes the formation of micropore defects and the embrittlement of the Laves phase.Hydrogen-promoted dislocation slip localization and hydrogen-induced reduction of interatomic bonding are the primary reasons for the Laves phase fracture and debonding at the Laves/γ-matrix interface.The coalescence of micropore defects ultimately leads to hydrogen-induced crack formation.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
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
The corrosion behavior of the laser powder bed fusion(LPBF)AZ91 magnesium alloy was investigated by comparing its longitudinal and transverse sections with the cast AZ91 alloy.Microstructural analysis revealed a fine,...The corrosion behavior of the laser powder bed fusion(LPBF)AZ91 magnesium alloy was investigated by comparing its longitudinal and transverse sections with the cast AZ91 alloy.Microstructural analysis revealed a fine,homogeneous Mg_(17)Al_(12) distribution in LPBF samples,contrasting with the network-like structure in the cast alloy.Electrochemical and hydrogen evolution tests demonstrated no significant anisotropy in LPBF sections,but they exhibited higher corrosion rates than the cast alloy.Potentiodynamic polarization and electrochemical impedance spectroscopy confirmed that the corrosion process was cathodically controlled by the Mg_(17)Al_(12) phase fraction.Scanning vibrating electrode technique further validated these findings,highlighting lower electrochemical activity in cast AZ91 alloy.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
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 AlMgScZr high-strength aluminum alloy fabricated by selective laser melting(SLM)technology exhibits a“bimodal microstructure”,resulting in significant non-uniform deformation during thermal deformation.This stud...The AlMgScZr high-strength aluminum alloy fabricated by selective laser melting(SLM)technology exhibits a“bimodal microstructure”,resulting in significant non-uniform deformation during thermal deformation.This study investigates the flow behavior of SLM-processed AlMgScZr aluminum alloy utilizing the Gleeble-1500D thermal simulation machine.The true stress-strain curves were amended based on the friction theory.Through determining the Zener-Hollomon parameters,the correlation between flow stress,deformation temperature,and strain rate during the high-temperature thermoplastic deformation of SLM-processed AlMgScZr aluminum alloy with a“bimodal microstructure”was established.In addition,the microstructural evolution during thermal deformation was analyzed.The results indicated that the predicted flow stress values obtained from the Arrhenius constitutive equation with coupled correction of thermal deformation parameters closely matched the experimental values.The correlation coefficient and the average absolute relative error of the corrected model were 0.999 and 2.766%,respectively,accurately predicting the thermoplastic deformation behavior of SLM-processed high-strength aluminum alloy with a“bimodal microstructure”.Furthermore,hot processing maps at different strains were established,identifying stable and unstable regions under different deformation conditions.Microstructural observations revealed different thermal deformation mechanisms under various deformation temperatures.Specifically,dynamic recrystallization characteristics dominated the microstructure at lower temperatures(300-360℃),while dynamic recovery was dominant at higher temperatures(390-500℃).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
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
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
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)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
基金National Natural Science Foundation of China(51504138,51674118,52271177)Hunan Provincial Natural Science Foundation of China(2023JJ50181)Supported by State Key Laboratory of Materials Processing and Die&Mould Technology,Huazhong University of Science and Technology(P2024-022)。
文摘To explore the formation mechanism of anisotropy in Ti-6Al-4V alloy fabricated by selective laser melting(SLM),the compressive mechanical properties,microhardness,microstructure,and crystallographic orientation of the alloy across different planes were investigated.The anisotropy of SLM-fabricated Ti-6Al-4V alloys was analyzed,and the electron backscatter diffraction technique was used to investigate the influence of different grain types and orientations on the stress-strain distribution at various scales.Results reveal that in room-temperature compression tests at a strain rate of 10^(-3) s^(-1),both the compressive yield strength and microhardness vary along the deposition direction,indicating a certain degree of mechanical property anisotropy.The alloy exhibits a columnar microstructure;along the deposition direction,the grains appear equiaxed,and they have internal hexagonal close-packed(hcp)α/α'martensitic structure.α'phase has a preferential orientation approximately along the<0001>direction.Anisotropy arises from the high aspect ratio of columnar grains,along with the weak texture of the microstructure and low symmetry of the hcp crystal structure.
基金supported by the National Natural Science Foundation of China(Grant No.12102133).
文摘Selective laser melting(SLM),as an additive manufacturing technology,has garnered widespread attention for its capability to fabricate components with complex geometries and to tailor the microstructure and mechanical properties under specific conditions.However,the intrinsic influence mechanism of microstructure formation under non-equilibrium solidification conditions in SLM processes has not been clearly revealed.In the present work,the influence of Al concentration and process parameters on the microstructure forming mechanism of Al_(x)CoCrFeNi HEAs prepared by SLM is investigated by molecular dynamics simulation method.The simulation results show that the difference in Al content significantly affects the microstructure formation of HEAs,including the growth rate and morphology of columnar crystals,stress distribution at grain boundaries,and defect structure.In addition,the results show that increasing the substrate temperature improves the solidification formability,reduces microstructural defects,and helps reduce residual stress in Al_(x)CoCrFeNi HEAs.By analyzing the influence of heat and solute flow in the molten pool on the growth of columnar crystals,it is found that spatial fluctuations in Al concentration during the non-equilibrium solidification process inhibit the high cooling rates induced by steep temperature gradients.These findings promote the understanding of the forming mechanism of microstructure in HEAs prepared by SLM and provide theoretical guidance for designing high-performance SLM-fabricated HEAs.
基金supported by the National Natural Science Foundation of China(Nos.U22B2067 and 52073176).
文摘350 keV He^(+) ions were injected into laser powder bed fusion(LPBF)-processed 304L stainless steel and traditional rolled 304L stainless steel with a flux of 1×10^(17) ions/cm^(2) at room temperature,followed by annealing at 750℃ for 10,100,and 300 h,respectively.The results showed that material swelling due to helium bubble coarsening was almost not observed in either the LPBF or rolled samples after 10 h of annealing duration.Rapid coarsening and swelling of bubbles occurred in the rolled samples,but only moderate bubble growth occurred in the LPBF sample after annealing for 100 h.After annealing for 300 h,the helium bubbles in both samples tended to grow steadily.For 10 h of annealing,the irradiated samples were in a disequilibrium state,and the apparent activation energy(E^(act))calculated by the Arrhenius model determined that helium atoms tended to diffuse through the displacement mechanism,and helium bubbles grew under the migration and coalescence(MC)mechanism.With annealing times over 100 h,the high-density dislocations and nano-oxide particles in the LPBF sample still had a strong trapping effect on the movement and growth of helium bubbles.After annealing for 300 h,the cellular subgrains in the LPBF sample decomposed,and the nano-oxide particles had no trapping effect on the helium bubbles.At this time,the dislocation structure played a primary role in suppressing the growth of helium bubbles,and the radiation resistance of the LPBF sample remained superior to that of the rolled samples.
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 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finncially supported by the National Natural Science Foundation of China(No.52075183)the Guangdong Basic and Applied Research Fundamental(No.2023A1515010692)the Key-Area Research and Development Program of Guangdong Province(Nos.2024B1111080002 and 2020B0404020004).
文摘Austenitic stainless steel(ASS)is a common material used in high-pressure hydrogen systems.Prolonged exposure to high-pressure hydrogen can cause hydrogen embrittlement(HE),raising significant safety concerns.Selective Laser Melting(SLM),known for its high precision,is a promising additive manufacturing technology that has been widely adopted across various industries.Studies have reported that under certain SLM manufacturing conditions and process parameters,the HE resistance of SLM ASS is significantly better than that of conventionally manufactured(CM)ASS,showing great potential for application in high-pressure hydrogen systems.Thus,studying the HE of SLM ASS is crucial for further improving the safety of high-pressure hydrogen systems.This paper provides an overview of the SLM process,reviews the mechanisms of HE and their synergistic effects,and analyzes the HE characteristics of SLM ASS.Additionally,it examines the influence of unique microstructures and SLM process variables on HE of SLM ASS and offers recommendations for future research to enhance the safety of high-pressure hydrogen systems.
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.
基金financially supported by the National Natural Science Foundation of China(Nos.U21A2044 and 52201060)CGN-USTB Joint Research and Development Center for Advanced Energy Materials and Service Safet.
文摘The effects of the Laves-decorated dendrite structure on the hydrogen-assisted cracking behavior of the SLM-718 alloy were investigated.The Laves phase exhibits a hydrogen desorption activation energy of 47.67±7.85 kJ mol^(-1).The results of in situ scanning Kelvin probe force microscopy and hydrogen microprint technique provide direct evidence of the hydrogen trapping by the Laves phase.The high-density dendrite walls consisting of entangled dislocations exhibit an inhibitory effect on hydrogen diffusion.Atomic-scale characterization reveals that dislocation stacking at the Laves/γ-matrix interface induces the formation of dislocation defects and a high-stress concentration in the Laves phase.The presence of hydrogen further promotes the formation of micropore defects and the embrittlement of the Laves phase.Hydrogen-promoted dislocation slip localization and hydrogen-induced reduction of interatomic bonding are the primary reasons for the Laves phase fracture and debonding at the Laves/γ-matrix interface.The coalescence of micropore defects ultimately leads to hydrogen-induced crack formation.
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the financial support under the Project PID2021-126166OB-I00 funded by MCIN/AEI/10.13039/501100011033 and by“ERDF A way of making Europe”(European Union)the Grant CNS2023-144665 funded by MCIN/AEI/10.13039/501100011033+1 种基金by the“European Union NextGenerationEU/PRTR.”the CSIC for the financial support under the project PIE-20216AT012.
文摘The corrosion behavior of the laser powder bed fusion(LPBF)AZ91 magnesium alloy was investigated by comparing its longitudinal and transverse sections with the cast AZ91 alloy.Microstructural analysis revealed a fine,homogeneous Mg_(17)Al_(12) distribution in LPBF samples,contrasting with the network-like structure in the cast alloy.Electrochemical and hydrogen evolution tests demonstrated no significant anisotropy in LPBF sections,but they exhibited higher corrosion rates than the cast alloy.Potentiodynamic polarization and electrochemical impedance spectroscopy confirmed that the corrosion process was cathodically controlled by the Mg_(17)Al_(12) phase fraction.Scanning vibrating electrode technique further validated these findings,highlighting lower electrochemical activity in cast AZ91 alloy.
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Project(22KJB430023)supported by the Natural Science Foundation for Colleges and Universities of Jiangsu Province,ChinaProject(1172922101)supported by the Youth Science and Technology Innovation Project of Jiangsu University of Science and Technology,China。
文摘The AlMgScZr high-strength aluminum alloy fabricated by selective laser melting(SLM)technology exhibits a“bimodal microstructure”,resulting in significant non-uniform deformation during thermal deformation.This study investigates the flow behavior of SLM-processed AlMgScZr aluminum alloy utilizing the Gleeble-1500D thermal simulation machine.The true stress-strain curves were amended based on the friction theory.Through determining the Zener-Hollomon parameters,the correlation between flow stress,deformation temperature,and strain rate during the high-temperature thermoplastic deformation of SLM-processed AlMgScZr aluminum alloy with a“bimodal microstructure”was established.In addition,the microstructural evolution during thermal deformation was analyzed.The results indicated that the predicted flow stress values obtained from the Arrhenius constitutive equation with coupled correction of thermal deformation parameters closely matched the experimental values.The correlation coefficient and the average absolute relative error of the corrected model were 0.999 and 2.766%,respectively,accurately predicting the thermoplastic deformation behavior of SLM-processed high-strength aluminum alloy with a“bimodal microstructure”.Furthermore,hot processing maps at different strains were established,identifying stable and unstable regions under different deformation conditions.Microstructural observations revealed different thermal deformation mechanisms under various deformation temperatures.Specifically,dynamic recrystallization characteristics dominated the microstructure at lower temperatures(300-360℃),while dynamic recovery was dominant at higher temperatures(390-500℃).
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.
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.
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.
