Titanium(Ti)alloys are widely used in high-tech fields like aerospace and biomedical engineering.Laser additive manufacturing(LAM),as an innovative technology,is the key driver for the development of Ti alloys.Despite...Titanium(Ti)alloys are widely used in high-tech fields like aerospace and biomedical engineering.Laser additive manufacturing(LAM),as an innovative technology,is the key driver for the development of Ti alloys.Despite the significant advancements in LAM of Ti alloys,there remain challenges that need further research and development efforts.To recap the potential of LAM high-performance Ti alloy,this article systematically reviews LAM Ti alloys with up-to-date information on process,materials,and properties.Several feasible solutions to advance LAM Ti alloys are reviewed,including intelligent process parameters optimization,LAM process innovation with auxiliary fields and novel Ti alloys customization for LAM.The auxiliary energy fields(e.g.thermal,acoustic,mechanical deformation and magnetic fields)can affect the melt pool dynamics and solidification behaviour during LAM of Ti alloys,altering microstructures and mechanical performances.Different kinds of novel Ti alloys customized for LAM,like peritecticα-Ti,eutectoid(α+β)-Ti,hybrid(α+β)-Ti,isomorphousβ-Ti and eutecticβ-Ti alloys are reviewed in detail.Furthermore,machine learning in accelerating the LAM process optimization and new materials development is also outlooked.This review summarizes the material properties and performance envelops and benchmarks the research achievements in LAM of Ti alloys.In addition,the perspectives and further trends in LAM of Ti alloys are also highlighted.展开更多
Metal matrix composites(MMCs)are frequently employed in various advanced industries due to their high modulus and strength,favorable wear and corrosion resistance,and other good properties at elevated temperatures.In ...Metal matrix composites(MMCs)are frequently employed in various advanced industries due to their high modulus and strength,favorable wear and corrosion resistance,and other good properties at elevated temperatures.In recent decades,additive manufacturing(AM)technology has garnered attention as a potential way for fabricating MMCs.This article provides a comprehensive review of recent endeavors and progress in AM of MMCs,encompassing available AM technologies,types of reinforcements,feedstock preparation,synthesis principles during the AM process,typical AM-produced MMCs,strengthening mechanisms,challenges,and future interests.Compared to conventionally manufactured MMCs,AM-produced MMCs exhibit more uniformly distributed reinforcements and refined microstructure,resulting in comparable or even better mechanical properties.In addition,AM technology can produce bulk MMCs with significantly low porosity and fabricate geometrically complex MMC components and MMC lattice structures.As reviewed,many AM-produced MMCs,such as Al matrix composites,Ti matrix composites,nickel matrix composites,Fe matrix composites,etc,have been successfully produced.The types and contents of reinforcements strongly influence the properties of AM-produced MMCs,the choice of AM technology,and the applied processing parameters.In these MMCs,four primary strengthening mechanisms have been identified:Hall–Petch strengthening,dislocation strengthening,load transfer strengthening,and Orowan strengthening.AM technologies offer advantages that enhance the properties of MMCs when compared with traditional fabrication methods.Despite the advantages above,further challenges of AM-produced MMCs are still faced,such as new methods and new technologies for investigating AM-produced MMCs,the intrinsic nature of MMCs coupled with AM technologies,and challenges in the AM processes.Therefore,the article concludes by discussing the challenges and future interests of AM of MMCs.展开更多
Beta Ti−35Nb sandwich-structured composites with various reinforcing layers were designed and produced using additive manufacturing(AM)to achieve a balance between light weight and high strength.The impact of reinforc...Beta Ti−35Nb sandwich-structured composites with various reinforcing layers were designed and produced using additive manufacturing(AM)to achieve a balance between light weight and high strength.The impact of reinforcing layers on the compressive deformation behavior of porous composites was investigated through micro-computed tomography(Micro-CT)and finite element method(FEM)analyses.The results indicate that the addition of reinforcement layers to sandwich structures can significantly enhance the compressive yield strength and energy absorption capacity of porous metal structures;Micro-CT in-situ observation shows that the strain of the porous structure without the reinforcing layer is concentrated in the middle region,while the strain of the porous structure with the reinforcing layer is uniformly distributed;FEM analysis reveals that the reinforcing layers can alter stress distribution and reduce stress concentration,thereby promoting uniform deformation of the porous structure.The addition of reinforcing layer increases the compressive yield strength of sandwich-structured composite materials by 124%under the condition of limited reduction of porosity,and the yield strength increases from 4.6 to 10.3 MPa.展开更多
Copper matrix composites doped with ceramic particles are known to effectively enhance the mechanical properties,thermal expansion behavior and high-temperature stability of copper while maintaining high thermal and e...Copper matrix composites doped with ceramic particles are known to effectively enhance the mechanical properties,thermal expansion behavior and high-temperature stability of copper while maintaining high thermal and electrical conductivity.This greatly expands the applications of copper as a functional material in thermal and conductive components,including electronic packaging materials and heat sinks,brushes,integrated circuit lead frames.So far,endeavors have been focusing on how to choose suitable ceramic components and fully exert strengthening effect of ceramic particles in the copper matrix.This article reviews and analyzes the effects of preparation techniques and the characteristics of ceramic particles,including ceramic particle content,size,morphology and interfacial bonding,on the diathermancy,electrical conductivity and mechanical behavior of copper matrix composites.The corresponding models and influencing mechanisms are also elaborated in depth.This review contributes to a deep understanding of the strengthening mechanisms and microstructural regulation of ceramic particle reinforced copper matrix composites.By more precise design and manipulation of composite microstructure,the comprehensive properties could be further improved to meet the growing demands of copper matrix composites in a wide range of application fields.展开更多
Solidification cracking issues during additive manufacturing(AM)severely prevent the rapid development and broad application of this method.In this work,a representative Co_(34)Cr_(32)Ni_(27)Al_(4)Ti_(3) high-entropy ...Solidification cracking issues during additive manufacturing(AM)severely prevent the rapid development and broad application of this method.In this work,a representative Co_(34)Cr_(32)Ni_(27)Al_(4)Ti_(3) high-entropy al-loy(HEA)susceptible to crack formation was fabricated by selective laser melting(SLM).As expected,many macroscopic cracks appeared.The crack issues were successfully solved after introducing a certain amount of Fe-based metallic glass(MG)powder as a glue during SLM.The effect of MG addition on the formation and distribution of defects in the SLM-processed HEA was quantitatively investigated.With an increasing mass fraction of the MG,the dominant defects transformed from cracks to lack of fusion(LOF)defects and finally disappeared.Intriguingly,the MG preferred to be segregated to the boundaries of the molten pool.Moreover,the coarse columnar crystals gradually transformed into equiaxed crystals in the molten pool and fine-equiaxed crystals at the edge of the molten pool,inhibiting the initiation of cracks and providing extra grain boundary strengthening.Furthermore,multiple precipitates are formed at the boundaries of cellular structures,which contribute significantly to strengthening.Compared to the brit-tle SLM-processed Co_(34)Cr_(32)Ni_(27)Al_(4)Ti_(3) HEA,the SLM-processed HEA composite exhibited a high ultimate tensile strength greater than 1.4 Ga and enhanced elongation.This work demonstrates that adding Fe-based MG powders as glues into SLM-processed HEAs may be an attractive method to heal cracks and simultaneously enhance the mechanical properties of additively manufactured products.展开更多
In actual physiological environments,bacteria can activate the immune system and release lactic acid.However,the detailed contribution of lactic acid to the passivation behavior of titanium(Ti)alloys is still unclear....In actual physiological environments,bacteria can activate the immune system and release lactic acid.However,the detailed contribution of lactic acid to the passivation behavior of titanium(Ti)alloys is still unclear.The current work investigated the in vitro passivation behavior of Ti-6Al-4V(TC4)alloys fabricated by laser powder bed fusion in Hank's solution with and without adding lactic acid.Electrochemical methods,inductively coupled plasma atomic emission spectrometer,and X-ray photoelectron spectroscopy were jointly used.Adding lactic acid decreases the corrosion resistance of samples by degrading the formed passive film.The film formed in the(lactic acid)-containing solution exhibits a higher level of oxygen vacancies and a lower thickness,attributed to the suppressed formation of Ti^(4+)transformed from Ti^(3+)and Ti^(2+).Moreover,the presence of lactic acid would increase the open circuit potential,relieve the ions release,and hinder the deposition of calcium phosphates within 24 h immersion.展开更多
The metal-based additive manufacturing(AM),also referred to as metal 3D printing,has drawn particular interest because it enables direct creation,aided by computationally-directed path design,of intricate components w...The metal-based additive manufacturing(AM),also referred to as metal 3D printing,has drawn particular interest because it enables direct creation,aided by computationally-directed path design,of intricate components with site-specific compositions and geometrical requirements as well as low buy-to-fly ratios.During the last two decades,the objective of this revolutionary technology has been shifting from only“rapid prototyping”to advanced manufacturing of special high-end products or devices,which,in many aspects,outperform conventional manufacturing technologies.For fusion-based AM,significant progress has been achieved in understanding the processing window of macroscopic scales,non-equilibrium metallurgy of mesoscale scales,and grain evolution of microscopic scales.Although the versatile capacity of AM facilitates new avenues for discovering advanced materials and structures,their potential has still not been fully explored.Given the unique non-equilibrium solidification during the AM process,coarse columnar grains with strong textures are usually developed along the build direction,which downgrades the mechanical performance.To push the limits of this digital manufacturing,this review attempts to provide in-depth and comprehensive overviews of the recent progress in understanding the evolution and control of the as-built microstructure that has been made recently and the challenges encountered during the AM process.展开更多
Additive manufacturing ofβ-type titanium alloy is expected to replace Ti-6Al-4V alloy in the field of orthopedic implantation because of their low elastic modulus,excellent corrosion resistance,and biocompatibility.A...Additive manufacturing ofβ-type titanium alloy is expected to replace Ti-6Al-4V alloy in the field of orthopedic implantation because of their low elastic modulus,excellent corrosion resistance,and biocompatibility.After briefly introducing the laser powder bed fusion(LPBF)process and physical phenomena,this paper reviews the recent progresses in LPBF-edβ-type Ti alloys.The strategies to strengthening and tougheningβ-type Ti alloys are critically reviewed.This is followed by the processing routes employed to achieve to low modulus for orthopedic applications,especially a new methodology for tailoring crystallographic orientation called multi-track coupled directional solidification.The effect of processing and compositions on performance metrics ofβ-type Ti alloys included corrosion behavior,and biocompatibility is reviewed.In the end,challenges in additive manufacturing ofβ-type Ti alloys in future are highlighted,with the aim to ensue clinical application of LPBF-edβ-type Ti alloys.展开更多
Additive manufacturing(AM),commonly known as 3D printing,has become a transformative technology that has a profound impact on various industrial sectors.AM encompasses a set of techniques for building objects layer by...Additive manufacturing(AM),commonly known as 3D printing,has become a transformative technology that has a profound impact on various industrial sectors.AM encompasses a set of techniques for building objects layer by layer from digital models.Unlike conventional subtractive manufacturing methods that involve removing material from large blocks,AM adds material incrementally,providing unprecedented design flexibility and efficiency.展开更多
As two kinds of well-known prominent high-performance alloys,metallic glasses(MGs)and high-entropy alloys(HEAs)have attracted increasing attention.Most of them contain multiple alloying components,demonstrate intrigui...As two kinds of well-known prominent high-performance alloys,metallic glasses(MGs)and high-entropy alloys(HEAs)have attracted increasing attention.Most of them contain multiple alloying components,demonstrate intriguing microstructures,and exhibit excellent properties;however,their unique performances are closely dependent on the fabrication process,although they are limited due to the need for rapid solidification during fabrication.On the other hand,additive manufacturing(AM)can be used to fabricate complex parts via rapid solidification,thus saving materials.These advantages provide AM with a great possibility to produce MG and HEA materials with tunable microstructures therefore properties,and corresponding parts with complex geometries,large dimensions,and more functions.This paper provides a comprehensive and systematic overview of the manufacturing and properties of MGs and HEAs using AM techniques.The correlation between MGs and HEAs with conventional manufacturing meth-ods and the difficulties encountered are retrospectively discussed.Afterward,this review specifically focuses on the recent research advances in MGs and HEAs fabricated using AM technologies.Then,various properties of the AM-fabricated MGs and HEAs are discussed.Finally,the remaining issues and potential solutions,challenges,and future directions on the AM of MGs and HEAs are also presented.展开更多
In this work, we report the effect of annealing in α＋β phase field on the fatigue properties of Ti-6A1-4V alloy meshes fabricated by electron beam melting. The results show that annealing at high temperature near t...In this work, we report the effect of annealing in α＋β phase field on the fatigue properties of Ti-6A1-4V alloy meshes fabricated by electron beam melting. The results show that annealing at high temperature near the phase boundary enhances the ductility of the brittle mesh struts due to the formation of coarse α lamellas with a large thickness/length ratio. Accordingly, the fatigue endurance ratio of the studied meshes increases to up to -0.6, which is much superior to that of the as-fabricated counterparts and comparable to those of dense materials.2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.展开更多
Although using elemental powder mixtures may provide broad alloy selection at low cost for selective laser melting(SLM), there is still a concern on the resultant microstructural and chemical homogeneity of the produc...Although using elemental powder mixtures may provide broad alloy selection at low cost for selective laser melting(SLM), there is still a concern on the resultant microstructural and chemical homogeneity of the produced parts. Hence, this work investigates the microstructure and mechanical properties of a SLM-produced Ti-35 Nb composite(in wt%) using elemental powder. The microstructural characteristics including ? phase, undissolved Nb particles and chemical homogeneity were detailed investigated.Nanoindentation revealed the presence of relatively soft undissolved Nb particles and weak interface bonding around Nb-rich regions in as-SLMed samples. Solid-solution treatment can not only improve chemical homogeneity but also enhance bonding through grain boundary strengthening, resulting in43 % increase in tensile elongation for the heat-treated Ti-35 Nb compared to the as-SLMed counterpart. The analyses of tensile fractures and shear bands further confirmed the correlation between the different phases and the ductility of Ti-35 Nb. In particular, the weak bonding between undissolved Nb and the matrix in the as-SLMed sample reduces its ductility while the ? grains in solid-solution treated Ti-Nb alloy can induce a relatively stable plastic flow therefore better ductility. This work sheds insight into the understanding of homogenization of microstructure and phases of SLM-produced alloys from an elemental powder mixture.展开更多
Although a variety of processing routes were developed to in-situ manipulate microstructure for fabricating high-performance Ti-6Al-4 V alloy by directed energy deposition(DED),the in-situ microstructural control abil...Although a variety of processing routes were developed to in-situ manipulate microstructure for fabricating high-performance Ti-6Al-4 V alloy by directed energy deposition(DED),the in-situ microstructural control ability has been limited and lead to a narrowed mechanical property control range.This work proved the microstructural correlation betweenβ-grains andα-laths resulting from the unique thermal characteristics of DED for the first time and solved such a dilemma through synchronous induction heating assisted laser deposition(SILD)technology.The results confirmed that the laser energy and inductive energy have a different effect on the solidification and solid phase transformation conditions.By adjusting the laser-induction parameters,the microstructural correlation can be tuned;theβ-grains andα-laths can be controlled relatively separately,thereby significantly enhancing the ductility of as-deposited sample(elongation from 14.2%to 20.1%).Furthermore,the mechanical properties of the tuned microstructures are even comparable to that of DED Ti-6Al-4 V with post heat treatment,which indicates that the potential of SILD to be a one-step manufacturing process to fabricate high performance components without post heat treatment.Furthermore,the tensile testing results of the tuned microstructures indicate thatα-lath size is more influential on the mechanical properties than theβ-grain size due to its stronger hindering effect on the slipping of dislocations.This work promotes the understanding of the microstructural formation mechanism in DED titanium alloy and proves that the combination of synchronous induction and laser can expand the ability to control the microstructure and properties of multi-layer deposition.展开更多
This work investigates the corrosion behavior of AlSilOMg alloy produced by selective laser melting(SLM) and the counterparts heat-treated at 450-550℃in 3.5 wt% NaCl solution.Electrochemical measurements and weight l...This work investigates the corrosion behavior of AlSilOMg alloy produced by selective laser melting(SLM) and the counterparts heat-treated at 450-550℃in 3.5 wt% NaCl solution.Electrochemical measurements and weight loss tests together with microstructural characterizations were conducted.The SLM-produced alloy displays a microstructure with a continuous network of Si particles,exhibiting superior corrosion behavior.After heat treatment,the Si particles are coarsened and isolated and A1 matrix dissolves into their surrounding area,thereby degrading the corrosion resistance properties.Therefore,the corrosion resistance of AlSilOMg alloy degrades with increasing the heat treatment temperature.展开更多
To overcome the dimension limits of immiscible alloys produced by traditional techniques and enhance their mechanical properties,bulk Cu-Fe-based immiscible alloy with abundant nanotwins and stacking faults was succes...To overcome the dimension limits of immiscible alloys produced by traditional techniques and enhance their mechanical properties,bulk Cu-Fe-based immiscible alloy with abundant nanotwins and stacking faults was successfully produced by selective laser melting(SLM).The SLM-produced bulk immiscible alloy displays a heterogeneous microstructure characterized by micro-scaledγ-Fe particles dispersed in fineε-Cu matrix with a high fraction(~92%)of high-angle grain boundaries.Interestingly,abundant nanotwins and stacking faults are generated in the interior of nano-scaledγ-Fe particles embedded withinε-Cu matrix.The heterogeneous interface of soft domains(ε-Cu)and hard domains(γ-Fe)not only induces the geometrically necessary dislocations(GNDs)but also affects the dislocation propagation during plastic deformation.Therefore,the bimodal heterogeneous interface,and the resistance of nanotwins and stacking faults to the propagation of partial dislocation make the bulk immiscible alloy exhibit an enhanced strength of~590 MPa and a good ductility of~8.9%.展开更多
This work studied the preparation of starting powder mixture influenced by milling time and its effect on the particle morphology （especially the shape） and, consequently, density and compression properties of in si...This work studied the preparation of starting powder mixture influenced by milling time and its effect on the particle morphology （especially the shape） and, consequently, density and compression properties of in situ Ti-TiB composite materials produced by selective laser melting （SLM） technology. Starting powder composite system was prepared by mixing 95 wt% commercially pure titanium （CP-Ti） and 5 wt% titanium diboride （TiB2） powders and subsequently milled for two different times （i.e. 2 h and 4 h）. The milled powder mixtures after 2 h and 4 h show nearly spherical and irregular shape, respectively. Subsequently, the resultant Ti-5 wt% TiB2 powder mixtures were used for SLM processing. Scanning electron microscopy image of the SLM-processed Ti-TiB composite samples show needle-shape TiB phase distributed across the Ti matrix, which is the product of an in-situ chemical reaction between Ti and TiB2 during SLM. The Ti-TiB composite samples prepared from 2 h and 4 h milled Ti-TiB2 powders show different relative densities of 99.5% and 95.1%, respectively. Also, the compression properties such as ultimate strength and compression strain for the 99.5% dense composite samples is 1421 MPa and 17.8%, respectively, which are superior to those （883 MPa and 5.5%, respectively） for the 95.1% dense sample. The results indicate that once Ti and TiB2 powders are connected firmly to each other and powder mixture of nearly spherical shape is obtained, there is no additional benefit in increasing the milling time and, instead, it has a negative effect on the density （i.e. increasing porosity level） of the Ti-TiB composite materials and their mechanical properties.展开更多
Ni-Cu nano-coatings were prepared by pulsed electroplating technique in the baths containing various amount of boric acid. Their microstructure, morphologies and corrosion resistance were characterized in detail. The ...Ni-Cu nano-coatings were prepared by pulsed electroplating technique in the baths containing various amount of boric acid. Their microstructure, morphologies and corrosion resistance were characterized in detail. The addition of boric acid strongly influences on the microstructure of the Ni-Cu coatings.The coating with a grain size of 130 nm, obtained from the bath containing 35 g L^-1 boric acid, shows the highest corrosion resistance. This is attributed to the low-valence Cu ion(Cu^+) additions in nickel oxide, which could significantly decrease the oxygen ion vacancy density in the passive film to form a more compact passive film. The higher Cu^+ additions and the lower diffusivity of point defects(D0) are responsible for the formation of more compact passive film on the coating obtained from the bath with 35 g L^-1 boric acid.展开更多
Electron beam melting （EBM） has been used to manufacture β-type Ti-24Nb-4Zr-8Sn porous compo- nents with 70% porosity, EBM-produced components have favorable structural features （i.e. smooth strut surfaces, fewer ...Electron beam melting （EBM） has been used to manufacture β-type Ti-24Nb-4Zr-8Sn porous compo- nents with 70% porosity, EBM-produced components have favorable structural features （i.e. smooth strut surfaces, fewer defects） and an （α ＋ β）-type microstructure, similar to that subjected to aging treat- ment. EBM-produced components exhibit more than twice the strength-to-modulus ratio of porous Ti- 6A1-4V components having the same porosity. The processing-microstructure-property relationship and deformation behavior of EBM-produced components are discussed in detail. Such porous titanium com- ponents composed of non-toxic elements and having high strength-to-modulus ratio are highly attractive for biomedical applications.展开更多
Biomedicalβ-phase Ti-Nb-Ta-Zr alloys usually exhibit low elastic modulus with inadequate strength.In the present work,a series of newly developed dual-phase Ti-xNb-yTa-2Zr(wt.%)alloys with high performance were inves...Biomedicalβ-phase Ti-Nb-Ta-Zr alloys usually exhibit low elastic modulus with inadequate strength.In the present work,a series of newly developed dual-phase Ti-xNb-yTa-2Zr(wt.%)alloys with high performance were investigated in which the stability ofβ-phase was reduced under the guidelines of ab initio calculations and d-electronic theory.The effects of Nb and Ta contents on the microstructure,compressive and tensile properties were investigated.Results demonstrate that the designed Ti-xNb-yTa-2Zr alloys exhibit typical characteristics ofα+βdual-phase microstructure.The microstructure of the alloys is more sensitive to Nb rather than Ta.The as-cast alloys exhibit needle-likeα′martensite at a lower Nb content of 3 wt.%and lamellarα′martensite at an Nb content of 5 wt.%.Among the alloys,the Ti-3Nb-13Ta-2Zr alloy shows the highest compressive strength(2270±10 MPa)and compressive strain(74.3%±0.4%).This superior performance is due to the combination ofα+βdual-phase microstructure and stressinducedα"martensite.Besides,lattice distortion caused by Ta element also contributes to the compressive properties.Nb and Ta contents of the alloys strongly affect Young's modulus and tensile properties after rolling.The as-rolled Ti-3Nb-13Ta-2Zr alloy exhibits much lower modulus due to lower Nb content as well as moreα"martensite andβphase with a good combination of low modulus and high strength among all the designed alloys.Atom probe tomography analysis reveals the element partitioning between theαandβphases in which Ta concentration is higher than Nb in theαphase.Also,the concentration of Ta is lower than that of Nb in theβphase,indicating that theβ-stability of Nb is higher than that of Ta.This work proposes modernα+βdual-phase Ti-xNb-yTa-2Zr alloys as a new concept to design novel biomedical Ti alloys with high performance.展开更多
A common challenge in direct energy deposition(DED)is eliminating the anisotropy in mechanical performance associated with microstructure and the formation of coarse columnar grains.In this work,a heterogeneous nuclea...A common challenge in direct energy deposition(DED)is eliminating the anisotropy in mechanical performance associated with microstructure and the formation of coarse columnar grains.In this work,a heterogeneous nucleation mechanism was introduced into the melt pool,and,from this mechanism,an almost fully equiaxed grain morphology was obtained in the DED of Ti-6 Al-3 Mo.Three types of grain morphologies in DED Ti-6 Al-3 Mo,including full columnar grains,near-equiaxed grains and almost fully equiaxed grains were obtained from premixed and satellite powder blends from Ti,6 wt.%Al and 3 wt.%Mo,respectively.Combined with the analysis of the interactions between powder particles and the melt pool in DED,the formation mechanism of the equiaxed grains caused by the incomplete melting of high melting point Mo particles was revealed.As the prior-βgrains transformed from coarse columnar grains to fine-equiaxed grains,the strong<100>fiber texture along the deposition direction was weakened,while the size of theα-laths in the prior-βgrains slightly decreased,and the selection ofα-variants was weakened.Due to the transformation of the prior-βgrains from coarse columnar grains to fine-equiaxed grains,the tensile strength of the deposited samples increased from 982 MPa to 1082 MPa,while the yield strength increased from 840 MPa to 922 MPa,and the elongation of the as-deposited alloy also increased from 9.0%to 9.8%,which confirmed that the presence of fine-equiaxed grains is beneficial to the strength and plasticity of the DED alloy.This work further demonstrates the role that satelliting powders can play in terms of enhancing the columnar to equiaxed transition(CET)behavior associated with DED.展开更多
基金financially supported by the Young Individual Research Grants(Grant No:M22K3c0097)Singapore RIE 2025 plan and Singapore Aerospace Programme Cycle 16(Grant No:M2215a0073)led by C Tan+2 种基金supported by the Singapore A*STAR Career Development Funds(Grant No:C210812047)the National Natural Science Foundation of China(52174361 and 52374385)the support by US NSF DMR-2104933。
文摘Titanium(Ti)alloys are widely used in high-tech fields like aerospace and biomedical engineering.Laser additive manufacturing(LAM),as an innovative technology,is the key driver for the development of Ti alloys.Despite the significant advancements in LAM of Ti alloys,there remain challenges that need further research and development efforts.To recap the potential of LAM high-performance Ti alloy,this article systematically reviews LAM Ti alloys with up-to-date information on process,materials,and properties.Several feasible solutions to advance LAM Ti alloys are reviewed,including intelligent process parameters optimization,LAM process innovation with auxiliary fields and novel Ti alloys customization for LAM.The auxiliary energy fields(e.g.thermal,acoustic,mechanical deformation and magnetic fields)can affect the melt pool dynamics and solidification behaviour during LAM of Ti alloys,altering microstructures and mechanical performances.Different kinds of novel Ti alloys customized for LAM,like peritecticα-Ti,eutectoid(α+β)-Ti,hybrid(α+β)-Ti,isomorphousβ-Ti and eutecticβ-Ti alloys are reviewed in detail.Furthermore,machine learning in accelerating the LAM process optimization and new materials development is also outlooked.This review summarizes the material properties and performance envelops and benchmarks the research achievements in LAM of Ti alloys.In addition,the perspectives and further trends in LAM of Ti alloys are also highlighted.
基金the financial support from the Australian Research Council through the Discovery Project(DP110101653 and DP130103592)Basic and Applied Basic Research Foundation of Guangdong Province,China(2022A1515140123).
文摘Metal matrix composites(MMCs)are frequently employed in various advanced industries due to their high modulus and strength,favorable wear and corrosion resistance,and other good properties at elevated temperatures.In recent decades,additive manufacturing(AM)technology has garnered attention as a potential way for fabricating MMCs.This article provides a comprehensive review of recent endeavors and progress in AM of MMCs,encompassing available AM technologies,types of reinforcements,feedstock preparation,synthesis principles during the AM process,typical AM-produced MMCs,strengthening mechanisms,challenges,and future interests.Compared to conventionally manufactured MMCs,AM-produced MMCs exhibit more uniformly distributed reinforcements and refined microstructure,resulting in comparable or even better mechanical properties.In addition,AM technology can produce bulk MMCs with significantly low porosity and fabricate geometrically complex MMC components and MMC lattice structures.As reviewed,many AM-produced MMCs,such as Al matrix composites,Ti matrix composites,nickel matrix composites,Fe matrix composites,etc,have been successfully produced.The types and contents of reinforcements strongly influence the properties of AM-produced MMCs,the choice of AM technology,and the applied processing parameters.In these MMCs,four primary strengthening mechanisms have been identified:Hall–Petch strengthening,dislocation strengthening,load transfer strengthening,and Orowan strengthening.AM technologies offer advantages that enhance the properties of MMCs when compared with traditional fabrication methods.Despite the advantages above,further challenges of AM-produced MMCs are still faced,such as new methods and new technologies for investigating AM-produced MMCs,the intrinsic nature of MMCs coupled with AM technologies,and challenges in the AM processes.Therefore,the article concludes by discussing the challenges and future interests of AM of MMCs.
基金the Hunan Young Scientific Innovative Talents Program,China(No.2020RC3040)Outstanding Youth Fund of Hunan Natural Science Foundation,China(Nos.2021JJ20011,2021JJ40600,2021JJ40590)the National Natural Science Foundation of China(Nos.52001030,52204371)..
文摘Beta Ti−35Nb sandwich-structured composites with various reinforcing layers were designed and produced using additive manufacturing(AM)to achieve a balance between light weight and high strength.The impact of reinforcing layers on the compressive deformation behavior of porous composites was investigated through micro-computed tomography(Micro-CT)and finite element method(FEM)analyses.The results indicate that the addition of reinforcement layers to sandwich structures can significantly enhance the compressive yield strength and energy absorption capacity of porous metal structures;Micro-CT in-situ observation shows that the strain of the porous structure without the reinforcing layer is concentrated in the middle region,while the strain of the porous structure with the reinforcing layer is uniformly distributed;FEM analysis reveals that the reinforcing layers can alter stress distribution and reduce stress concentration,thereby promoting uniform deformation of the porous structure.The addition of reinforcing layer increases the compressive yield strength of sandwich-structured composite materials by 124%under the condition of limited reduction of porosity,and the yield strength increases from 4.6 to 10.3 MPa.
基金supported by National Natural Science Foundation of China(No.51971101)Science and Technology Development Program of Jilin Province,China(20230201146G X)Exploration Foundation of State Key Laboratory of Automotive Simulation and Control(asclzytsxm-202015)。
文摘Copper matrix composites doped with ceramic particles are known to effectively enhance the mechanical properties,thermal expansion behavior and high-temperature stability of copper while maintaining high thermal and electrical conductivity.This greatly expands the applications of copper as a functional material in thermal and conductive components,including electronic packaging materials and heat sinks,brushes,integrated circuit lead frames.So far,endeavors have been focusing on how to choose suitable ceramic components and fully exert strengthening effect of ceramic particles in the copper matrix.This article reviews and analyzes the effects of preparation techniques and the characteristics of ceramic particles,including ceramic particle content,size,morphology and interfacial bonding,on the diathermancy,electrical conductivity and mechanical behavior of copper matrix composites.The corresponding models and influencing mechanisms are also elaborated in depth.This review contributes to a deep understanding of the strengthening mechanisms and microstructural regulation of ceramic particle reinforced copper matrix composites.By more precise design and manipulation of composite microstructure,the comprehensive properties could be further improved to meet the growing demands of copper matrix composites in a wide range of application fields.
基金National Natural Science Foundation of China(Nos.51971180,51871132,51971179 and 52271037)New R&D Institution Construction Program of Guangdong Province,China(No.2019B090905009)+2 种基金Shenzhen Fundamental Research Program,China(No.JCYJ20210324122203010)Shaanxi Provincial Science and Technology Program,China(No.2023-JC-ZD-23)Foreign Senior Talents Program of Guangdong Province,China and the Fundamental Research Funds for the Central Universities of China(No.D5000230131).
文摘Solidification cracking issues during additive manufacturing(AM)severely prevent the rapid development and broad application of this method.In this work,a representative Co_(34)Cr_(32)Ni_(27)Al_(4)Ti_(3) high-entropy al-loy(HEA)susceptible to crack formation was fabricated by selective laser melting(SLM).As expected,many macroscopic cracks appeared.The crack issues were successfully solved after introducing a certain amount of Fe-based metallic glass(MG)powder as a glue during SLM.The effect of MG addition on the formation and distribution of defects in the SLM-processed HEA was quantitatively investigated.With an increasing mass fraction of the MG,the dominant defects transformed from cracks to lack of fusion(LOF)defects and finally disappeared.Intriguingly,the MG preferred to be segregated to the boundaries of the molten pool.Moreover,the coarse columnar crystals gradually transformed into equiaxed crystals in the molten pool and fine-equiaxed crystals at the edge of the molten pool,inhibiting the initiation of cracks and providing extra grain boundary strengthening.Furthermore,multiple precipitates are formed at the boundaries of cellular structures,which contribute significantly to strengthening.Compared to the brit-tle SLM-processed Co_(34)Cr_(32)Ni_(27)Al_(4)Ti_(3) HEA,the SLM-processed HEA composite exhibited a high ultimate tensile strength greater than 1.4 Ga and enhanced elongation.This work demonstrates that adding Fe-based MG powders as glues into SLM-processed HEAs may be an attractive method to heal cracks and simultaneously enhance the mechanical properties of additively manufactured products.
基金The authors acknowledge the Fundamental Research Program of Jiangsu Province(BK20201000)the Australian Research Council through the Discovery Project(DP110101653,DP130103592)+1 种基金the Basic and Applied Basic Research Foundation of Guangdong Province,China(2022A1515140123,2021A1515110729)the Foshan(Southern China)Institute for New Materials(2021AYF25017).The authors are grateful to Jinling Zhu.
文摘In actual physiological environments,bacteria can activate the immune system and release lactic acid.However,the detailed contribution of lactic acid to the passivation behavior of titanium(Ti)alloys is still unclear.The current work investigated the in vitro passivation behavior of Ti-6Al-4V(TC4)alloys fabricated by laser powder bed fusion in Hank's solution with and without adding lactic acid.Electrochemical methods,inductively coupled plasma atomic emission spectrometer,and X-ray photoelectron spectroscopy were jointly used.Adding lactic acid decreases the corrosion resistance of samples by degrading the formed passive film.The film formed in the(lactic acid)-containing solution exhibits a higher level of oxygen vacancies and a lower thickness,attributed to the suppressed formation of Ti^(4+)transformed from Ti^(3+)and Ti^(2+).Moreover,the presence of lactic acid would increase the open circuit potential,relieve the ions release,and hinder the deposition of calcium phosphates within 24 h immersion.
基金This work is supported by the National Key Research and Development Program of China(Grant No.2022YFB4600500)the National Natural Science Foundation of China(Grant Nos.52235006 and 52025053).
文摘The metal-based additive manufacturing(AM),also referred to as metal 3D printing,has drawn particular interest because it enables direct creation,aided by computationally-directed path design,of intricate components with site-specific compositions and geometrical requirements as well as low buy-to-fly ratios.During the last two decades,the objective of this revolutionary technology has been shifting from only“rapid prototyping”to advanced manufacturing of special high-end products or devices,which,in many aspects,outperform conventional manufacturing technologies.For fusion-based AM,significant progress has been achieved in understanding the processing window of macroscopic scales,non-equilibrium metallurgy of mesoscale scales,and grain evolution of microscopic scales.Although the versatile capacity of AM facilitates new avenues for discovering advanced materials and structures,their potential has still not been fully explored.Given the unique non-equilibrium solidification during the AM process,coarse columnar grains with strong textures are usually developed along the build direction,which downgrades the mechanical performance.To push the limits of this digital manufacturing,this review attempts to provide in-depth and comprehensive overviews of the recent progress in understanding the evolution and control of the as-built microstructure that has been made recently and the challenges encountered during the AM process.
基金This work was supported financially by the National Natural Science Foundation of China(Nos.52304397 and U19A2085)the Guangdong Basic and Applied Basic Research Foundation(Nos.2022B1515120082 and 2019B030302010)+1 种基金the Guangdong Science and Technology Innovation Project(No.2021TX06C111)the Optical Valley Science Research Project,WEHDZ(No.2019001).
文摘Additive manufacturing ofβ-type titanium alloy is expected to replace Ti-6Al-4V alloy in the field of orthopedic implantation because of their low elastic modulus,excellent corrosion resistance,and biocompatibility.After briefly introducing the laser powder bed fusion(LPBF)process and physical phenomena,this paper reviews the recent progresses in LPBF-edβ-type Ti alloys.The strategies to strengthening and tougheningβ-type Ti alloys are critically reviewed.This is followed by the processing routes employed to achieve to low modulus for orthopedic applications,especially a new methodology for tailoring crystallographic orientation called multi-track coupled directional solidification.The effect of processing and compositions on performance metrics ofβ-type Ti alloys included corrosion behavior,and biocompatibility is reviewed.In the end,challenges in additive manufacturing ofβ-type Ti alloys in future are highlighted,with the aim to ensue clinical application of LPBF-edβ-type Ti alloys.
文摘Additive manufacturing(AM),commonly known as 3D printing,has become a transformative technology that has a profound impact on various industrial sectors.AM encompasses a set of techniques for building objects layer by layer from digital models.Unlike conventional subtractive manufacturing methods that involve removing material from large blocks,AM adds material incrementally,providing unprecedented design flexibility and efficiency.
基金support from the Na-tional Key Research&Development Program of China(No.2021YFF0600502)the National Natural Science Foundation of China(No.52171165)the Australian Research Council through Discovery Project(No.DP130103592).
文摘As two kinds of well-known prominent high-performance alloys,metallic glasses(MGs)and high-entropy alloys(HEAs)have attracted increasing attention.Most of them contain multiple alloying components,demonstrate intriguing microstructures,and exhibit excellent properties;however,their unique performances are closely dependent on the fabrication process,although they are limited due to the need for rapid solidification during fabrication.On the other hand,additive manufacturing(AM)can be used to fabricate complex parts via rapid solidification,thus saving materials.These advantages provide AM with a great possibility to produce MG and HEA materials with tunable microstructures therefore properties,and corresponding parts with complex geometries,large dimensions,and more functions.This paper provides a comprehensive and systematic overview of the manufacturing and properties of MGs and HEAs using AM techniques.The correlation between MGs and HEAs with conventional manufacturing meth-ods and the difficulties encountered are retrospectively discussed.Afterward,this review specifically focuses on the recent research advances in MGs and HEAs fabricated using AM technologies.Then,various properties of the AM-fabricated MGs and HEAs are discussed.Finally,the remaining issues and potential solutions,challenges,and future directions on the AM of MGs and HEAs are also presented.
基金supported partially by the National Key Research and Development Program of China (No. 2017YFC1104903)the Key Research Program of Frontier Sciences, CAS (QYZDJ-SSWJSC031-02)+1 种基金the National Natural Science Foundation of China (No. 51631007)the Liaoning Science and Technology Project (No. 2015225014)
文摘In this work, we report the effect of annealing in α＋β phase field on the fatigue properties of Ti-6A1-4V alloy meshes fabricated by electron beam melting. The results show that annealing at high temperature near the phase boundary enhances the ductility of the brittle mesh struts due to the formation of coarse α lamellas with a large thickness/length ratio. Accordingly, the fatigue endurance ratio of the studied meshes increases to up to -0.6, which is much superior to that of the as-fabricated counterparts and comparable to those of dense materials.2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.
基金support of the ECU Postgraduate Research AwardForrest Research Foundation Ph D Scholarship+1 种基金the Australian Government Research Training Program Scholarship(ECU)the facilities,and the scientific and technical assistance of the Australian Microscopy&Microanalysis Research Facility at the Centre for Microscopy,Characterisation&Analysis,The University of Western Australia,a facility funded by the University,State and Commonwealth Governments。
文摘Although using elemental powder mixtures may provide broad alloy selection at low cost for selective laser melting(SLM), there is still a concern on the resultant microstructural and chemical homogeneity of the produced parts. Hence, this work investigates the microstructure and mechanical properties of a SLM-produced Ti-35 Nb composite(in wt%) using elemental powder. The microstructural characteristics including ? phase, undissolved Nb particles and chemical homogeneity were detailed investigated.Nanoindentation revealed the presence of relatively soft undissolved Nb particles and weak interface bonding around Nb-rich regions in as-SLMed samples. Solid-solution treatment can not only improve chemical homogeneity but also enhance bonding through grain boundary strengthening, resulting in43 % increase in tensile elongation for the heat-treated Ti-35 Nb compared to the as-SLMed counterpart. The analyses of tensile fractures and shear bands further confirmed the correlation between the different phases and the ductility of Ti-35 Nb. In particular, the weak bonding between undissolved Nb and the matrix in the as-SLMed sample reduces its ductility while the ? grains in solid-solution treated Ti-Nb alloy can induce a relatively stable plastic flow therefore better ductility. This work sheds insight into the understanding of homogenization of microstructure and phases of SLM-produced alloys from an elemental powder mixture.
基金supported by the National Natural Science Foundation of China(Grant No.51475380)the National Key Research and Development Program of China(No.2018YFB1106302)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.3102020MS0402)the fund of the State Key Laboratory of Solidification Processing in NWPU(Grant No.SKLSP202110)。
文摘Although a variety of processing routes were developed to in-situ manipulate microstructure for fabricating high-performance Ti-6Al-4 V alloy by directed energy deposition(DED),the in-situ microstructural control ability has been limited and lead to a narrowed mechanical property control range.This work proved the microstructural correlation betweenβ-grains andα-laths resulting from the unique thermal characteristics of DED for the first time and solved such a dilemma through synchronous induction heating assisted laser deposition(SILD)technology.The results confirmed that the laser energy and inductive energy have a different effect on the solidification and solid phase transformation conditions.By adjusting the laser-induction parameters,the microstructural correlation can be tuned;theβ-grains andα-laths can be controlled relatively separately,thereby significantly enhancing the ductility of as-deposited sample(elongation from 14.2%to 20.1%).Furthermore,the mechanical properties of the tuned microstructures are even comparable to that of DED Ti-6Al-4 V with post heat treatment,which indicates that the potential of SILD to be a one-step manufacturing process to fabricate high performance components without post heat treatment.Furthermore,the tensile testing results of the tuned microstructures indicate thatα-lath size is more influential on the mechanical properties than theβ-grain size due to its stronger hindering effect on the slipping of dislocations.This work promotes the understanding of the microstructural formation mechanism in DED titanium alloy and proves that the combination of synchronous induction and laser can expand the ability to control the microstructure and properties of multi-layer deposition.
基金supported financially by the Project of Shanghai Science and Technology Commission (No. 14DZ2261000)the Australian Research Council’s Project funding scheme (No. DP110101653).
文摘This work investigates the corrosion behavior of AlSilOMg alloy produced by selective laser melting(SLM) and the counterparts heat-treated at 450-550℃in 3.5 wt% NaCl solution.Electrochemical measurements and weight loss tests together with microstructural characterizations were conducted.The SLM-produced alloy displays a microstructure with a continuous network of Si particles,exhibiting superior corrosion behavior.After heat treatment,the Si particles are coarsened and isolated and A1 matrix dissolves into their surrounding area,thereby degrading the corrosion resistance properties.Therefore,the corrosion resistance of AlSilOMg alloy degrades with increasing the heat treatment temperature.
基金financially supported by the Projects of MOE Key Lab of Disaster Forecast and Control in Engineering in Jinan University(No.20200904006)the Guangdong Basic and Applied Basic Research Foundation(No.2020B1515420004)。
文摘To overcome the dimension limits of immiscible alloys produced by traditional techniques and enhance their mechanical properties,bulk Cu-Fe-based immiscible alloy with abundant nanotwins and stacking faults was successfully produced by selective laser melting(SLM).The SLM-produced bulk immiscible alloy displays a heterogeneous microstructure characterized by micro-scaledγ-Fe particles dispersed in fineε-Cu matrix with a high fraction(~92%)of high-angle grain boundaries.Interestingly,abundant nanotwins and stacking faults are generated in the interior of nano-scaledγ-Fe particles embedded withinε-Cu matrix.The heterogeneous interface of soft domains(ε-Cu)and hard domains(γ-Fe)not only induces the geometrically necessary dislocations(GNDs)but also affects the dislocation propagation during plastic deformation.Therefore,the bimodal heterogeneous interface,and the resistance of nanotwins and stacking faults to the propagation of partial dislocation make the bulk immiscible alloy exhibit an enhanced strength of~590 MPa and a good ductility of~8.9%.
基金supported by the Australian Research Council’s Projects Funding Scheme (No. DP110101653)the European Commission (BioTiNet-ITN G.A. No.264635)the Deutsche Forschungsgemeinschaft (SFB/Transregio 79, Project M1)
文摘This work studied the preparation of starting powder mixture influenced by milling time and its effect on the particle morphology （especially the shape） and, consequently, density and compression properties of in situ Ti-TiB composite materials produced by selective laser melting （SLM） technology. Starting powder composite system was prepared by mixing 95 wt% commercially pure titanium （CP-Ti） and 5 wt% titanium diboride （TiB2） powders and subsequently milled for two different times （i.e. 2 h and 4 h）. The milled powder mixtures after 2 h and 4 h show nearly spherical and irregular shape, respectively. Subsequently, the resultant Ti-5 wt% TiB2 powder mixtures were used for SLM processing. Scanning electron microscopy image of the SLM-processed Ti-TiB composite samples show needle-shape TiB phase distributed across the Ti matrix, which is the product of an in-situ chemical reaction between Ti and TiB2 during SLM. The Ti-TiB composite samples prepared from 2 h and 4 h milled Ti-TiB2 powders show different relative densities of 99.5% and 95.1%, respectively. Also, the compression properties such as ultimate strength and compression strain for the 99.5% dense composite samples is 1421 MPa and 17.8%, respectively, which are superior to those （883 MPa and 5.5%, respectively） for the 95.1% dense sample. The results indicate that once Ti and TiB2 powders are connected firmly to each other and powder mixture of nearly spherical shape is obtained, there is no additional benefit in increasing the milling time and, instead, it has a negative effect on the density （i.e. increasing porosity level） of the Ti-TiB composite materials and their mechanical properties.
基金financially supported by the National Natural Science Foundation of China (Nos. 51771061 and 51571067)National Basic Research Program of China (No. 2014CB643301)+4 种基金National Natural Science Foundation of Heilongjiang Province, China (No. E2016022)the Fundamental Research Founds for the Central Universities (No. HEUCFG201838)the Ministry of Science and Technology of China (No. 2012FY113000)Key Laboratory of Superlight Materials and Surface Technology (Harbin Engineering University), Ministry of Educationthe Chinese Scholarship Council in conjunction with Harbin Engineering University & the Viet Nam Maritime University
文摘Ni-Cu nano-coatings were prepared by pulsed electroplating technique in the baths containing various amount of boric acid. Their microstructure, morphologies and corrosion resistance were characterized in detail. The addition of boric acid strongly influences on the microstructure of the Ni-Cu coatings.The coating with a grain size of 130 nm, obtained from the bath containing 35 g L^-1 boric acid, shows the highest corrosion resistance. This is attributed to the low-valence Cu ion(Cu^+) additions in nickel oxide, which could significantly decrease the oxygen ion vacancy density in the passive film to form a more compact passive film. The higher Cu^+ additions and the lower diffusivity of point defects(D0) are responsible for the formation of more compact passive film on the coating obtained from the bath with 35 g L^-1 boric acid.
基金supported partially by the National High-Tech R&D Program of China(863 Program,No.2015AA033702)the National Basic Research Program of China(Nos.2012CB619103 and 2012CB933901)+1 种基金the National Natural Science Foundation of China(Nos.51271182 and 51501200)the Australian Research Council Discovery Project(Nos.DP110101653 and DP130103592)
文摘Electron beam melting （EBM） has been used to manufacture β-type Ti-24Nb-4Zr-8Sn porous compo- nents with 70% porosity, EBM-produced components have favorable structural features （i.e. smooth strut surfaces, fewer defects） and an （α ＋ β）-type microstructure, similar to that subjected to aging treat- ment. EBM-produced components exhibit more than twice the strength-to-modulus ratio of porous Ti- 6A1-4V components having the same porosity. The processing-microstructure-property relationship and deformation behavior of EBM-produced components are discussed in detail. Such porous titanium com- ponents composed of non-toxic elements and having high strength-to-modulus ratio are highly attractive for biomedical applications.
基金financially supported by the National Natural Science Foundation of China(Nos.52011530181 and 51831011)the Shanghai Science and Technology Commission(No.20S31900100)。
文摘Biomedicalβ-phase Ti-Nb-Ta-Zr alloys usually exhibit low elastic modulus with inadequate strength.In the present work,a series of newly developed dual-phase Ti-xNb-yTa-2Zr(wt.%)alloys with high performance were investigated in which the stability ofβ-phase was reduced under the guidelines of ab initio calculations and d-electronic theory.The effects of Nb and Ta contents on the microstructure,compressive and tensile properties were investigated.Results demonstrate that the designed Ti-xNb-yTa-2Zr alloys exhibit typical characteristics ofα+βdual-phase microstructure.The microstructure of the alloys is more sensitive to Nb rather than Ta.The as-cast alloys exhibit needle-likeα′martensite at a lower Nb content of 3 wt.%and lamellarα′martensite at an Nb content of 5 wt.%.Among the alloys,the Ti-3Nb-13Ta-2Zr alloy shows the highest compressive strength(2270±10 MPa)and compressive strain(74.3%±0.4%).This superior performance is due to the combination ofα+βdual-phase microstructure and stressinducedα"martensite.Besides,lattice distortion caused by Ta element also contributes to the compressive properties.Nb and Ta contents of the alloys strongly affect Young's modulus and tensile properties after rolling.The as-rolled Ti-3Nb-13Ta-2Zr alloy exhibits much lower modulus due to lower Nb content as well as moreα"martensite andβphase with a good combination of low modulus and high strength among all the designed alloys.Atom probe tomography analysis reveals the element partitioning between theαandβphases in which Ta concentration is higher than Nb in theαphase.Also,the concentration of Ta is lower than that of Nb in theβphase,indicating that theβ-stability of Nb is higher than that of Ta.This work proposes modernα+βdual-phase Ti-xNb-yTa-2Zr alloys as a new concept to design novel biomedical Ti alloys with high performance.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB1100103)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2020JM-239)+2 种基金the National Natural Science Foundation of China(No.51475380)the Fundamental Research Funds for the Central Universities CHD(No.300102319208)the National Training Program of Innovation and Entrepreneurship for Undergraduates(No.S202010710142)。
文摘A common challenge in direct energy deposition(DED)is eliminating the anisotropy in mechanical performance associated with microstructure and the formation of coarse columnar grains.In this work,a heterogeneous nucleation mechanism was introduced into the melt pool,and,from this mechanism,an almost fully equiaxed grain morphology was obtained in the DED of Ti-6 Al-3 Mo.Three types of grain morphologies in DED Ti-6 Al-3 Mo,including full columnar grains,near-equiaxed grains and almost fully equiaxed grains were obtained from premixed and satellite powder blends from Ti,6 wt.%Al and 3 wt.%Mo,respectively.Combined with the analysis of the interactions between powder particles and the melt pool in DED,the formation mechanism of the equiaxed grains caused by the incomplete melting of high melting point Mo particles was revealed.As the prior-βgrains transformed from coarse columnar grains to fine-equiaxed grains,the strong<100>fiber texture along the deposition direction was weakened,while the size of theα-laths in the prior-βgrains slightly decreased,and the selection ofα-variants was weakened.Due to the transformation of the prior-βgrains from coarse columnar grains to fine-equiaxed grains,the tensile strength of the deposited samples increased from 982 MPa to 1082 MPa,while the yield strength increased from 840 MPa to 922 MPa,and the elongation of the as-deposited alloy also increased from 9.0%to 9.8%,which confirmed that the presence of fine-equiaxed grains is beneficial to the strength and plasticity of the DED alloy.This work further demonstrates the role that satelliting powders can play in terms of enhancing the columnar to equiaxed transition(CET)behavior associated with DED.
