Lightweight aluminum(Al)alloys have been widely used in frontier fields like aerospace and automotive industries,which attracts great interest in additive manufacturing(AM)to process high-value Al parts.As a mainstrea...Lightweight aluminum(Al)alloys have been widely used in frontier fields like aerospace and automotive industries,which attracts great interest in additive manufacturing(AM)to process high-value Al parts.As a mainstream AM technique,laser-directed energy deposition(LDED)shows good scalability to meet the requirements for large-format component manufacturing and repair.However,LDED Al alloys are highly challenging due to their inherent poor printability(e.g.low laser absorption,high oxidation sensitivity and cracking tendency).To further promote the development of LDED high-performance Al alloys,this review offers a deep understanding of the challenges and strategies to improve printability in LDED Al alloys.The porosity,cracking,distortion,inclusions,element evaporation and resultant inferior mechanical properties(worse than laser powder bed fusion)are the key challenges in LDED Al alloys.Processing parameter optimizations,in-situ alloy design,reinforcing particle addition and field assistance are the efficient approaches to improving the printability and performance of LDED Al alloys.The underlying correlations between processes,alloy innovation,characteristic microstructures,and achievable performances in LDED Al alloys are discussed.The benchmark mechanical properties and primary strengthening mechanism of LDED Al alloys are summarized.This review aims to provide a critical and in-depth evaluation of current progress in LDED Al alloys.Future opportunities and perspectives in LDED high-performance Al alloys are also outlined.展开更多
The effect of scanning strategy on the microstructure and properties of GH3536 Ni-based superalloy prepared by Laser Powder Bed Fusion was investigated,for the purpose of building high quality hydrocyclone part.The re...The effect of scanning strategy on the microstructure and properties of GH3536 Ni-based superalloy prepared by Laser Powder Bed Fusion was investigated,for the purpose of building high quality hydrocyclone part.The results show that the strength of Z67°(a zone with 67°hatch angle strategy)specimen is the highest among the four scanning strategies(0°,67°,90°and Z67°),with yield strength and tensile strength of 681 MPa and 837 MPa,respectively.Selective orientation of crystals occurs during the forming process because the longitudinal section of the specimen exhibits a high texture strength in(001).As the stretching proceeds,the plastic deformation mechanism of the specimen gradually changes from slip to twin-dominated,a substantial amount of twinning is observed in the region where the deformation of the specimen reaches 80%.The additive manufacturing simulation suite:Ansys Additive is used to simulate the stress and deformation of the part during the process,and the displacement results are consistent with the experimental phenomena.According to the simulation results,the structure design is optimized and the surface quality of the part is improved.The results show that the support of the part is more reasonable when the overhang angle is 45°.展开更多
CoCrMoW alloys with different nitrogen(N)additions(0,0.05,0.1,and 0.2 wt%)were prepared via laser powder bed fusion(LPBF).The effects of N content on the microstructure and mechanical properties were investigated.The ...CoCrMoW alloys with different nitrogen(N)additions(0,0.05,0.1,and 0.2 wt%)were prepared via laser powder bed fusion(LPBF).The effects of N content on the microstructure and mechanical properties were investigated.The results indicate that the LPBFed CoCrMoW alloy with 0.1 wt%N addition(0.1 N alloy)shows the best combination of mechanical properties with a yield strength of~983 MPa and an elongation of~19%.Both the LPBF process and the N addition impose great effects on suppressing theγtoεmartensitic transformation,resulting in a decrease in the width and amount ofεlaths/stacking faults.Besides,the N addition promotes the segregation of elements Mo,W,and Si along the cellular sub-grain boundaries(CBs),forming fine and discontinuous precipitates rich in Mo,W and Si along the CBs in the 0.1 N alloy,but dense and continuous(Mo,W)5Si_(3)precipitates along the CBs in the 0.2 N alloy.The(Mo,W)5Si_(3)precipitates with a tetragonal structure were observed and characterized for the first time in the Co-Cr based alloys.The negative mixing enthalpy between the non-metallic elements N,Si and the metallic elements Mo,W,Cr,and the rapid solidification induced segregation of high melting point elements such as Mo and W along CBs during LPBF process,synergistically contribute to the chemical heterogeneity in the alloys.The pure FCC matrix,the slightly increased segregation of Mo,W,Si elements and fine precipitates along the CBs contribute to the good combination of strength and elongation of the 0.1 N alloy.However,though pure FCC phase was present in the 0.2 N alloy,the dense and continuous(Mo,W)5Si_(3)precipitates along CBs acted as nucleation sites for cracks,deteriorating the elongation of the alloy.Overall,it is possible to tune the mechanical properties of the LPBFed CoCrMoW alloy by adjusting the local chemical heterogeneity.展开更多
Ni51Ti49 at.%bulk was additively manufactured by laser-directed energy deposition(DED)to reveal the microstructure evolution,phase distribution,and mechanical properties.It is found that the localized remelting,reheat...Ni51Ti49 at.%bulk was additively manufactured by laser-directed energy deposition(DED)to reveal the microstructure evolution,phase distribution,and mechanical properties.It is found that the localized remelting,reheating,and heat accumulation during DED leads to the spatial heterogeneous distribution of columnar crystal and equiaxed crystal,a gradient distribution of Ni4Ti3 precipitates along the building direction,and preferential formation of Ni4Ti3 precipitates in the columnar zone.The austenite transformation finish temperature(Af)varies from-12.65℃(Z=33 mm)to 60.35℃(Z=10 mm),corresponding to tensile yield strength(σ0.2)changed from 120±30 MPa to 570±20 MPa,and functional properties changed from shape memory effect to superelasticity at room temperature.The sample in the Z=20.4 mm height has the best plasticity of 9.6%and the best recoverable strain of 4.2%.This work provided insights and guidelines for the spatial characterization of DEDed NiTi.展开更多
The surface of copper-chromium alloy was processed by Al-Si-Ni multi-permeation and friction stir processing,and the microstructure and mechanical properties of the surface layer were tested by scanning electron micro...The surface of copper-chromium alloy was processed by Al-Si-Ni multi-permeation and friction stir processing,and the microstructure and mechanical properties of the surface layer were tested by scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),microhardness tester and friction testing machine.The results show that Al,Si and Ni elements are fully permeated into the surface of copper-chromium alloy after multielement co-infiltration and friction stir processing.In the observation of the microstructures,we found that the reticular structure is fragmented and distributed in the stir zone region.Microstructure becomes finer and grains refinement.The micro hardness of the copper-chromium alloy increased to 129 HV,44.9%higher than that of the original matrix.The main reasons of microhardness enhancement are solid solution strengthening,fine grains strengthening and dispersion strengthening.The friction test results show that the friction coefficient is basically stable at 0.69 and the wear mass is only 0.0017 g after 10 min of friction test.The improvement of wear resistance was attributed to the increase of microhardness of the alloy surface.展开更多
Oxide dispersion strengthened(ODS)superalloys are widely used in aerospace and nuclear reactors due to their exceptional creep strength and fatigue crack resistance at elevated temperature.In this work,an ODS NiCrFeY ...Oxide dispersion strengthened(ODS)superalloys are widely used in aerospace and nuclear reactors due to their exceptional creep strength and fatigue crack resistance at elevated temperature.In this work,an ODS NiCrFeY alloy for high temperature applications was fabricated by laser powder bed fusion(L-PBF).The microstructure and mechanical properties at room and elevated temperature of the L-PBF processed ODS NiCrFeY alloy were investigated.It was demonstrated that equiaxed grains with large fraction of low angle grain boundaries and cellular structures with high density of dislocations were obtained in the as-built alloy.Dispersed Y_(2)O_(3)nanoparticles were in-situ formed in the ODS NiCrFeY alloy.Most of the Y_(2)O_(3)nanoparticles were located at the cellular walls and pinned with a large number of dislocations.Due to the strengthening effects by dispersed Y_(2)O_(3)nanoparticles and fine cellular structures,the ODS NiCrFeY alloy showed high ultimate tensile strength of 810,560 and 250MPa at room temperature,600℃ and 800℃,respectively.展开更多
Selective laser melting(SLM)of aluminium alloys for lightweight application is arousing widespread interest,but the available alloy compositions are limited due to unsatisfactory mechanical performances.The rapid soli...Selective laser melting(SLM)of aluminium alloys for lightweight application is arousing widespread interest,but the available alloy compositions are limited due to unsatisfactory mechanical performances.The rapid solidifi cation of SLM provides a pathway to design a novel alloy composition with extended solubility.This strategy is demonstrated by an additively manufactured novel Al–2.51 Mn–2.71 Mg–0.55 Sc–0.29 Cu–0.31 Zn alloy with the supersaturated solid solution in the present study.The microstructure of as-build sample is characterized with multi-modal grains with the fi ne equiaxed grain(FEG,~800 nm)at molten pool boundaries,coarse equiaxed grain(CEG,~2μm)and columnar dendrites(CD,~4μm)inside the molten pool,which relates to the precipitations type and distribution.It is observable that Al 3(Sc,Zr)precipitation particles with the size of~50 nm are dispersed in the FEG zone,while the interior of CEG shows no Al3(Sc,Zr)particle which only exists at the CEG boundaries.Regardless of FEG,CEG or CD,the slender Al6 Mn precipitation with the length of~500 nm is distributed along the grain boundaries.Meanwhile,a lot of vacancies and thickness fringes are detected in the FEG zone,which confi rms the supersaturated solid solution in laser rapid solidifi cation.The ultimate tensile strength and yield strength of the as-printed sample are~380 MPa and~330 MPa,respectively,with elongation~14%,which increase to~440 MPa and~410 MPa with a reduction of elongation to~9%after heat treatment.展开更多
Eutectic high-entropy alloys,composed of FCC/B2 phases with a narrow solidification interval and excel-lent fluidity,have become a new hotspot in additive manufacturing.Nevertheless,their microstructures exhibit signi...Eutectic high-entropy alloys,composed of FCC/B2 phases with a narrow solidification interval and excel-lent fluidity,have become a new hotspot in additive manufacturing.Nevertheless,their microstructures exhibit significant sensitivity to processing parameters,feedstocks,and composition,ultimately limiting the alloys’engineering applications.Here,a hypereutectic Al_(0.7)CoCrFeNi_(2.4)alloy with a low cracking sus-ceptibility index was designed by Thermo-Calc calculation and fabricated by laser powder bed fusion.Results show that the as-printed Al_(0.7)CoCrFeNi_(2.4)alloy manifests a stable cellular structure,coupled with appreciable ultimate tensile strength(≥1200 MPa)and ductility(≥20%)over a wide range of process-ing parameters.After aging at 800℃for 30 min,outstanding strength(1500 MPa)and elongation(15%)were obtained.Considerable mechanical properties after aging stem from a triple strengthening mecha-nism,i.e.,L1_(2) nanoprecipitates and rod-shaped B2 particles within the FCC matrix,along with Cr-enriched spherical nanoparticles in the B2 phase.Meanwhile,hierarchical structure,i.e.,FCC dominated matrix,a discontinuous B2 phase,a precipitation-free zone in the B2 phase,and a K-S orientation relationship be-tween FCC and B2,facilitate to maintain excellent plasticity.These results guide designing HEAs by AM with controllable microstructures and outstanding mechanical properties for industrial applications.展开更多
In this paper,the effects of rare earth oxides on the micro structure and mechanical properties of nickelbased superalloys prepared by high-energy beam processing technology were critically studied.The focus is on the...In this paper,the effects of rare earth oxides on the micro structure and mechanical properties of nickelbased superalloys prepared by high-energy beam processing technology were critically studied.The focus is on the optimal amount of rare earth oxides that can produce ideal results.Special attention was paid to their main strengthening mechanisms,including solid solution strengthening mainly in the form of solid solution dissolved in the nickel-based alloy and improving the microstructure of the alloy by grain refinement or fine grain strengthening produced by homogenizing the distribution phase.Y_(2)O_(3),La_(2)O_(3) and CeO_(2) rare earth oxides can also improve the fluidity of the alloy molten pool and reduce the segregation of alloying elements.These advantages can significantly improve the mechanical properties of the alloy.Thereafter,this paper outlines the future research directions of rare earth oxides,aiming to expand their application potential.展开更多
碱性水电解(AWE)作为一种具有工业应用前景的绿色制氢方法,能够用来改善能源短缺和环境污染问题.然而,由于电极材料昂贵且效率低下,这种方法生产氢气的效率比较低.本文采用块状AlCoCrFeNi高熵合金作为碱性电解水的有效电极.研究发现通...碱性水电解(AWE)作为一种具有工业应用前景的绿色制氢方法,能够用来改善能源短缺和环境污染问题.然而,由于电极材料昂贵且效率低下,这种方法生产氢气的效率比较低.本文采用块状AlCoCrFeNi高熵合金作为碱性电解水的有效电极.研究发现通过快速阳极氧化(5 min)处理的高熵合金可以同时对析氢和析氧反应(HER和OER)具有超高的催化活性,只需要880和845 m V的过电位就可以达到-500 mA cm-2(HER)和500 mA cm-2(OER)的电流密度.特别地,该催化剂只需要3.00 V就可以达到500 mA cm-2的全解水电流密度,并且在此电流密度下表现出超过100小时的出色稳定性.我们的研究表明,阳极氧化的块体AlCoCrFeNi高熵合金作为高效催化剂在工业水电解制氢中具有广阔的应用前景,有望用于缓解环境问题和能源危机.展开更多
In order to refine the microstructure and improve the performance of direct energy deposited(DED)additively manufactured Al–Mg–Sc–Zr alloy,TiC-modified Al–Mg–Sc–Zr composites were prepared by DED and the effect ...In order to refine the microstructure and improve the performance of direct energy deposited(DED)additively manufactured Al–Mg–Sc–Zr alloy,TiC-modified Al–Mg–Sc–Zr composites were prepared by DED and the effect of TiC content on the microstructure and performance was studied.In the absence of TiC particle,the microstructure of Al–Mg–Sc–Zr alloy prepared by DED consisted of fine grains with average size of 8.36μm,and well-dispersed nano-Al;(Sc,Zr)particles inside the grains and Mg;Si phase along the grain boundaries.With the addition of 1 wt%TiC,the microstructure of TiC/Al–Mg–Sc–Zr prepared by DED became finer apparently compared with that without TiC;while the further increase of TiC content to 3 wt%,the microstructure of TiC/Al–Mg–Sc–Zr prepared by DED became coarser with appearance of a new kind of needle-like(Ti,Zr);Si;phase.Also,the addition of TiC decreased the porosity of Al–Mg–Sc–Zr prepared by DED.Simultaneously,after the addition of TiC,the tensile strength increased from 283.25 MPa to 344.98–361.51 MPa,and the elongation increased from 3.61%to 9.58–14.10%.The potential mechanism of the microstructure evolution and strength improvement was discussed.This research will provide new insights into the available metal matrix composites by laser additive manufacturing(LAM).展开更多
With the rapid development of indium tin oxide(ITO)in the electronic display industry,choosing which raw powders to prepare high-quality ITO targets has always been a controversial topic.In the work,in order to clearl...With the rapid development of indium tin oxide(ITO)in the electronic display industry,choosing which raw powders to prepare high-quality ITO targets has always been a controversial topic.In the work,in order to clearly understand the effect of the raw powders on the microstructure and properties of ITO targets and thin films,tin-doped indium oxide(dITO)and In_(2)O_3-SnO_(2)mixed(mITO)powders were chosen to prepare ITO targets for depositing the films and a comparative study on their microstructure and properties was conducted.It is found that,(1)dITO targets possess a higher solid solubility of tin in indium oxide and more uniform elemental distribution,while there are a higher density,a finer grain size and a higher mass ratio of In_(2)O_3 to SnO_(2)for the mITO targets;(2)dITO films with more coarser columnar grains and a rougher surface prefer to grow along the[100]direction in an Ar atmosphere;(3)the conductive property of ITO films only depends on the doping amount of tin and is independent of the raw powders and the preparation process of the target source;(4)dITO films possess the superior optical property and narrower optical band gap;(5)the etching property of mITO films is superior to that of dITO films due to the lower solid solubility of tin in indium oxide.展开更多
An Al-Mg-Sc-Zr alloy was additively manufactured by laser direct energy deposition(DED)under different laser powers,and the microstructures and mechanical properties of the as-deposited samples were investigated.The s...An Al-Mg-Sc-Zr alloy was additively manufactured by laser direct energy deposition(DED)under different laser powers,and the microstructures and mechanical properties of the as-deposited samples were investigated.The samples showed a fully equiaxed grain structure with grain sizes of 2–30μm.Most of the blocky primary Al3(Sc,Zr)-precipitated phases(<5μm)were arranged along the grain boundaries.A small amount of fine granular secondary Al3(Sc,Zr)phases(<0.5μm)were precipitated owing to the cyclic heat treatment during the DED forming process.According to the EBSD(Electron backscatter diffraction)results,the texture index and strength of the sample were only slightly greater than 1,indicating that the material structure exhibited a certain but not obvious anisotropy.The sample in the horizontal direction had better yield strength,tensile strength,and elogation properties(399.87 MPa,220.96 MPa,9.13%)than that in the building direction(385.40 MPa,219.40 MPa,8.24%),although the sample in the〈XOZ〉plane had the finest equiaxed grains.The ductility of the〈XOZ〉sample deteriorated as the number of pores increased.展开更多
Hydrogen pores in laser additive manufacturing(LAM)aluminum alloys have long been a major challenge for its application.In this study,the formation mechanisms of hydrogen pores and its kinetic behaviors were systemati...Hydrogen pores in laser additive manufacturing(LAM)aluminum alloys have long been a major challenge for its application.In this study,the formation mechanisms of hydrogen pores and its kinetic behaviors were systematically investigated in laser directed energy deposited(L-DED)AlMgScZr alloy.The results indicated that hydrogen pores accumulated layer by layer at the melt pool boundaries,due to the high nucleation rate and insufficient time to escape of hydrogen pores at the melt pool boundaries.Dring the AlMgScZr powder at 150°C/4 h enabled the significant decrease of moisture content from 0.0520 wt%to 0.0096 wt%,while the porosity of the L-DED sample only decreased from 0.51%to 0.36%.The increase of laser power decreased the porosity of L-DED sample.Except the L-DED parameters,the alloy composition exerted a more significant influence on hydrogen porosity.When the Mg content increased from 9 wt%to 14 wt%,the porosity exhibited an increase from 0.36%to 0.52%.Conversely,the incorporation and subsequent augmentation of Si content resulted in a significant reduction in porosity,reaching as low as 0.15%with an increase to 2 wt%.The solubility and diffusion coefficient of[H]in Al-Mg-Sc-Zr melt with different Mg and Si contents were calculated by density functional theory(DFT).It was observed that increasing the Si content led to a decrease in the nucleation zone for hydrogen pores and reduced poros-ity.A comprehensive porosity inhibition strategy that combines powder drying,process optimization,and composition regulation have been developed.展开更多
基金supported by the 2022 MTC Young Individual Research Grants(Grant No.M22K3c0097)the Singapore Research,Innovation and Enterprise(RIE)2025 PlanSingapore Aerospace Programme Cycle 16(Grant No.M2215a0073)。
文摘Lightweight aluminum(Al)alloys have been widely used in frontier fields like aerospace and automotive industries,which attracts great interest in additive manufacturing(AM)to process high-value Al parts.As a mainstream AM technique,laser-directed energy deposition(LDED)shows good scalability to meet the requirements for large-format component manufacturing and repair.However,LDED Al alloys are highly challenging due to their inherent poor printability(e.g.low laser absorption,high oxidation sensitivity and cracking tendency).To further promote the development of LDED high-performance Al alloys,this review offers a deep understanding of the challenges and strategies to improve printability in LDED Al alloys.The porosity,cracking,distortion,inclusions,element evaporation and resultant inferior mechanical properties(worse than laser powder bed fusion)are the key challenges in LDED Al alloys.Processing parameter optimizations,in-situ alloy design,reinforcing particle addition and field assistance are the efficient approaches to improving the printability and performance of LDED Al alloys.The underlying correlations between processes,alloy innovation,characteristic microstructures,and achievable performances in LDED Al alloys are discussed.The benchmark mechanical properties and primary strengthening mechanism of LDED Al alloys are summarized.This review aims to provide a critical and in-depth evaluation of current progress in LDED Al alloys.Future opportunities and perspectives in LDED high-performance Al alloys are also outlined.
基金the financial support of Technology Innovation Leadership Program for High-tech Industries(2020GK2031)Hunan Innovation Platform and Talent Plan(2022RC3033)Natural Science Foundation of Shandong Province(ZR2020ZD04).
文摘The effect of scanning strategy on the microstructure and properties of GH3536 Ni-based superalloy prepared by Laser Powder Bed Fusion was investigated,for the purpose of building high quality hydrocyclone part.The results show that the strength of Z67°(a zone with 67°hatch angle strategy)specimen is the highest among the four scanning strategies(0°,67°,90°and Z67°),with yield strength and tensile strength of 681 MPa and 837 MPa,respectively.Selective orientation of crystals occurs during the forming process because the longitudinal section of the specimen exhibits a high texture strength in(001).As the stretching proceeds,the plastic deformation mechanism of the specimen gradually changes from slip to twin-dominated,a substantial amount of twinning is observed in the region where the deformation of the specimen reaches 80%.The additive manufacturing simulation suite:Ansys Additive is used to simulate the stress and deformation of the part during the process,and the displacement results are consistent with the experimental phenomena.According to the simulation results,the structure design is optimized and the surface quality of the part is improved.The results show that the support of the part is more reasonable when the overhang angle is 45°.
基金the financial support from National Natural Science Foundation of China[grant number 52171130(S.Ni)]Huxiang Youth Talents Support Program[grant number 2021RC3002(S.Ni)]+1 种基金the financial support from the Research Office and Research Institute of Advanced Manufacturing of the Hong Kong Polytechnic University[grant numbers P0039966 and P0041361]support from the Royal Society in the UK under Grant No.IES\R3\223190.
文摘CoCrMoW alloys with different nitrogen(N)additions(0,0.05,0.1,and 0.2 wt%)were prepared via laser powder bed fusion(LPBF).The effects of N content on the microstructure and mechanical properties were investigated.The results indicate that the LPBFed CoCrMoW alloy with 0.1 wt%N addition(0.1 N alloy)shows the best combination of mechanical properties with a yield strength of~983 MPa and an elongation of~19%.Both the LPBF process and the N addition impose great effects on suppressing theγtoεmartensitic transformation,resulting in a decrease in the width and amount ofεlaths/stacking faults.Besides,the N addition promotes the segregation of elements Mo,W,and Si along the cellular sub-grain boundaries(CBs),forming fine and discontinuous precipitates rich in Mo,W and Si along the CBs in the 0.1 N alloy,but dense and continuous(Mo,W)5Si_(3)precipitates along the CBs in the 0.2 N alloy.The(Mo,W)5Si_(3)precipitates with a tetragonal structure were observed and characterized for the first time in the Co-Cr based alloys.The negative mixing enthalpy between the non-metallic elements N,Si and the metallic elements Mo,W,Cr,and the rapid solidification induced segregation of high melting point elements such as Mo and W along CBs during LPBF process,synergistically contribute to the chemical heterogeneity in the alloys.The pure FCC matrix,the slightly increased segregation of Mo,W,Si elements and fine precipitates along the CBs contribute to the good combination of strength and elongation of the 0.1 N alloy.However,though pure FCC phase was present in the 0.2 N alloy,the dense and continuous(Mo,W)5Si_(3)precipitates along CBs acted as nucleation sites for cracks,deteriorating the elongation of the alloy.Overall,it is possible to tune the mechanical properties of the LPBFed CoCrMoW alloy by adjusting the local chemical heterogeneity.
基金the financial support of the Hunan Innovation Platform and Talent Plan(2022RC3033)Natural Science Foundation of Shandong Province(ZR2020ZD04)Ganzhou Science and Technology Planning Project(Grant No.Ganshikefa[2019]60)。
文摘Ni51Ti49 at.%bulk was additively manufactured by laser-directed energy deposition(DED)to reveal the microstructure evolution,phase distribution,and mechanical properties.It is found that the localized remelting,reheating,and heat accumulation during DED leads to the spatial heterogeneous distribution of columnar crystal and equiaxed crystal,a gradient distribution of Ni4Ti3 precipitates along the building direction,and preferential formation of Ni4Ti3 precipitates in the columnar zone.The austenite transformation finish temperature(Af)varies from-12.65℃(Z=33 mm)to 60.35℃(Z=10 mm),corresponding to tensile yield strength(σ0.2)changed from 120±30 MPa to 570±20 MPa,and functional properties changed from shape memory effect to superelasticity at room temperature.The sample in the Z=20.4 mm height has the best plasticity of 9.6%and the best recoverable strain of 4.2%.This work provided insights and guidelines for the spatial characterization of DEDed NiTi.
基金financial support from the National Natural Science Foundation of China (No. 51571214)Science Project of Shenzhen (JCYJ20180508151903646)
文摘The surface of copper-chromium alloy was processed by Al-Si-Ni multi-permeation and friction stir processing,and the microstructure and mechanical properties of the surface layer were tested by scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),microhardness tester and friction testing machine.The results show that Al,Si and Ni elements are fully permeated into the surface of copper-chromium alloy after multielement co-infiltration and friction stir processing.In the observation of the microstructures,we found that the reticular structure is fragmented and distributed in the stir zone region.Microstructure becomes finer and grains refinement.The micro hardness of the copper-chromium alloy increased to 129 HV,44.9%higher than that of the original matrix.The main reasons of microhardness enhancement are solid solution strengthening,fine grains strengthening and dispersion strengthening.The friction test results show that the friction coefficient is basically stable at 0.69 and the wear mass is only 0.0017 g after 10 min of friction test.The improvement of wear resistance was attributed to the increase of microhardness of the alloy surface.
基金supports from the Key-Area Research and Development Program of Guangdong Province,China(No.2019B010943001)the Transformation and Industrialization Plan of Scientific and Technological Achievements of Hunan Province,China(No.2020GK2031)+2 种基金the High-Tech Industrial Science and Technology Innovation Leading Plan of Hunan Province,China(No.2020GK4018)the fund of State Key Laboratory of Powder Metallurgy,Central South University,Chinathe Innovation Center of Nuclear Materials for National Defense Industry,China(No.ICNM-2020-YZ-02).
文摘Oxide dispersion strengthened(ODS)superalloys are widely used in aerospace and nuclear reactors due to their exceptional creep strength and fatigue crack resistance at elevated temperature.In this work,an ODS NiCrFeY alloy for high temperature applications was fabricated by laser powder bed fusion(L-PBF).The microstructure and mechanical properties at room and elevated temperature of the L-PBF processed ODS NiCrFeY alloy were investigated.It was demonstrated that equiaxed grains with large fraction of low angle grain boundaries and cellular structures with high density of dislocations were obtained in the as-built alloy.Dispersed Y_(2)O_(3)nanoparticles were in-situ formed in the ODS NiCrFeY alloy.Most of the Y_(2)O_(3)nanoparticles were located at the cellular walls and pinned with a large number of dislocations.Due to the strengthening effects by dispersed Y_(2)O_(3)nanoparticles and fine cellular structures,the ODS NiCrFeY alloy showed high ultimate tensile strength of 810,560 and 250MPa at room temperature,600℃ and 800℃,respectively.
基金the National Natural Science Foundation of China(51871249)the Guangxi Key Research and Development Programme(Guike AB19050002)+3 种基金the Science and Technology Planning Project of Shenzhen(JCYJ20180508151903646)the Hunan Science Fund for Distinguished Young Scholars(2020JJ2046)Natural Science Foundation of Shandong Province(ZR2020ZD04)the Huxiang Youth Talent Support Programme(2018RS3007)。
文摘Selective laser melting(SLM)of aluminium alloys for lightweight application is arousing widespread interest,but the available alloy compositions are limited due to unsatisfactory mechanical performances.The rapid solidifi cation of SLM provides a pathway to design a novel alloy composition with extended solubility.This strategy is demonstrated by an additively manufactured novel Al–2.51 Mn–2.71 Mg–0.55 Sc–0.29 Cu–0.31 Zn alloy with the supersaturated solid solution in the present study.The microstructure of as-build sample is characterized with multi-modal grains with the fi ne equiaxed grain(FEG,~800 nm)at molten pool boundaries,coarse equiaxed grain(CEG,~2μm)and columnar dendrites(CD,~4μm)inside the molten pool,which relates to the precipitations type and distribution.It is observable that Al 3(Sc,Zr)precipitation particles with the size of~50 nm are dispersed in the FEG zone,while the interior of CEG shows no Al3(Sc,Zr)particle which only exists at the CEG boundaries.Regardless of FEG,CEG or CD,the slender Al6 Mn precipitation with the length of~500 nm is distributed along the grain boundaries.Meanwhile,a lot of vacancies and thickness fringes are detected in the FEG zone,which confi rms the supersaturated solid solution in laser rapid solidifi cation.The ultimate tensile strength and yield strength of the as-printed sample are~380 MPa and~330 MPa,respectively,with elongation~14%,which increase to~440 MPa and~410 MPa with a reduction of elongation to~9%after heat treatment.
基金The authors would like to acknowledge experimental help and invaluable discussions from Shanzi Yu,Xianglong Li,Zhongliang Shu,Shichao Liu,Ruifeng Xu,Pengda Niu,Dan Li,Rou Ding,Min Liu,Haoyang Li,and Taomei Zhang.The authors would also like to acknowledge the financial support from the Natural science foundation of China(No.52271046,No.52171052)the Natural Science Foundation of Hunan Province,China(No.2022JJ20061,No.2023JJ30684)+4 种基金the Key R&D Program of Guangdong Province,China(No.2019B010943001)the Transformation and Industrializa-tion Plan of Scientific and Technological Achievements of Hunan Province,China(No.2020GK2031)the National Natural Science Foundation of China(No.52171052)the funding from State Key Laboratory of Powder Metallurgy,Central South Universitythe Fundamental Research Funds for the Central Universities of Central South University.
文摘Eutectic high-entropy alloys,composed of FCC/B2 phases with a narrow solidification interval and excel-lent fluidity,have become a new hotspot in additive manufacturing.Nevertheless,their microstructures exhibit significant sensitivity to processing parameters,feedstocks,and composition,ultimately limiting the alloys’engineering applications.Here,a hypereutectic Al_(0.7)CoCrFeNi_(2.4)alloy with a low cracking sus-ceptibility index was designed by Thermo-Calc calculation and fabricated by laser powder bed fusion.Results show that the as-printed Al_(0.7)CoCrFeNi_(2.4)alloy manifests a stable cellular structure,coupled with appreciable ultimate tensile strength(≥1200 MPa)and ductility(≥20%)over a wide range of process-ing parameters.After aging at 800℃for 30 min,outstanding strength(1500 MPa)and elongation(15%)were obtained.Considerable mechanical properties after aging stem from a triple strengthening mecha-nism,i.e.,L1_(2) nanoprecipitates and rod-shaped B2 particles within the FCC matrix,along with Cr-enriched spherical nanoparticles in the B2 phase.Meanwhile,hierarchical structure,i.e.,FCC dominated matrix,a discontinuous B2 phase,a precipitation-free zone in the B2 phase,and a K-S orientation relationship be-tween FCC and B2,facilitate to maintain excellent plasticity.These results guide designing HEAs by AM with controllable microstructures and outstanding mechanical properties for industrial applications.
基金Project supported by China Postdoctoral Science Foundation(2021M7010380)the Natural Science Foundation of Shanghai (20ZR1422700)Class Ⅲ Peak Discipline of Shanghai-Materials Science and Engineering (High-Energy Beam Intelligent Processing and Green Manufacturing)。
文摘In this paper,the effects of rare earth oxides on the micro structure and mechanical properties of nickelbased superalloys prepared by high-energy beam processing technology were critically studied.The focus is on the optimal amount of rare earth oxides that can produce ideal results.Special attention was paid to their main strengthening mechanisms,including solid solution strengthening mainly in the form of solid solution dissolved in the nickel-based alloy and improving the microstructure of the alloy by grain refinement or fine grain strengthening produced by homogenizing the distribution phase.Y_(2)O_(3),La_(2)O_(3) and CeO_(2) rare earth oxides can also improve the fluidity of the alloy molten pool and reduce the segregation of alloying elements.These advantages can significantly improve the mechanical properties of the alloy.Thereafter,this paper outlines the future research directions of rare earth oxides,aiming to expand their application potential.
基金supported by the Multi-Year Research Grants(MYRG2020-00207-IAPME)from the University of Macaothe Science and Technology Development Fund from Macao SAR(FDCT)(0125/2018/A3,0081/2019/AMJ,0033/2019/AMJ,0102/2019/A2,and 0154/2019/A3)+1 种基金the Nature Science Foundation of Shandong Province(ZR2020ZD04)Hunan Science Fund for Distinguished Young Scholars(2020JJ2046).
文摘碱性水电解(AWE)作为一种具有工业应用前景的绿色制氢方法,能够用来改善能源短缺和环境污染问题.然而,由于电极材料昂贵且效率低下,这种方法生产氢气的效率比较低.本文采用块状AlCoCrFeNi高熵合金作为碱性电解水的有效电极.研究发现通过快速阳极氧化(5 min)处理的高熵合金可以同时对析氢和析氧反应(HER和OER)具有超高的催化活性,只需要880和845 m V的过电位就可以达到-500 mA cm-2(HER)和500 mA cm-2(OER)的电流密度.特别地,该催化剂只需要3.00 V就可以达到500 mA cm-2的全解水电流密度,并且在此电流密度下表现出超过100小时的出色稳定性.我们的研究表明,阳极氧化的块体AlCoCrFeNi高熵合金作为高效催化剂在工业水电解制氢中具有广阔的应用前景,有望用于缓解环境问题和能源危机.
基金the National Natural Science Foundation of China(No.51871249)the Science Foundation of Shangdong Province(ZR2020ZD04)+4 种基金the Science and Technology Plan Project of Shenzhen(JCYJ20180508151903646)the Hunan distinguished author(2020JJ2046)the Hunan key R&D Plan(2020WK2027)the Large-scale Instruments and Equipments of Central South University(CSUZC202110)the Science and Technology Planning Project of Guangxi(Guike AB 19050002)。
文摘In order to refine the microstructure and improve the performance of direct energy deposited(DED)additively manufactured Al–Mg–Sc–Zr alloy,TiC-modified Al–Mg–Sc–Zr composites were prepared by DED and the effect of TiC content on the microstructure and performance was studied.In the absence of TiC particle,the microstructure of Al–Mg–Sc–Zr alloy prepared by DED consisted of fine grains with average size of 8.36μm,and well-dispersed nano-Al;(Sc,Zr)particles inside the grains and Mg;Si phase along the grain boundaries.With the addition of 1 wt%TiC,the microstructure of TiC/Al–Mg–Sc–Zr prepared by DED became finer apparently compared with that without TiC;while the further increase of TiC content to 3 wt%,the microstructure of TiC/Al–Mg–Sc–Zr prepared by DED became coarser with appearance of a new kind of needle-like(Ti,Zr);Si;phase.Also,the addition of TiC decreased the porosity of Al–Mg–Sc–Zr prepared by DED.Simultaneously,after the addition of TiC,the tensile strength increased from 283.25 MPa to 344.98–361.51 MPa,and the elongation increased from 3.61%to 9.58–14.10%.The potential mechanism of the microstructure evolution and strength improvement was discussed.This research will provide new insights into the available metal matrix composites by laser additive manufacturing(LAM).
基金financially supported by the National Key R&D Program of China(No.2017YFB0305401)the National Natural Science Foundation of China(Nos.51874369 and 51871249)the Huxiang Young Talents Plan(No.2018RS3007)。
文摘With the rapid development of indium tin oxide(ITO)in the electronic display industry,choosing which raw powders to prepare high-quality ITO targets has always been a controversial topic.In the work,in order to clearly understand the effect of the raw powders on the microstructure and properties of ITO targets and thin films,tin-doped indium oxide(dITO)and In_(2)O_3-SnO_(2)mixed(mITO)powders were chosen to prepare ITO targets for depositing the films and a comparative study on their microstructure and properties was conducted.It is found that,(1)dITO targets possess a higher solid solubility of tin in indium oxide and more uniform elemental distribution,while there are a higher density,a finer grain size and a higher mass ratio of In_(2)O_3 to SnO_(2)for the mITO targets;(2)dITO films with more coarser columnar grains and a rougher surface prefer to grow along the[100]direction in an Ar atmosphere;(3)the conductive property of ITO films only depends on the doping amount of tin and is independent of the raw powders and the preparation process of the target source;(4)dITO films possess the superior optical property and narrower optical band gap;(5)the etching property of mITO films is superior to that of dITO films due to the lower solid solubility of tin in indium oxide.
基金National Natural Science Foundation of China(Grant No.U21B2073)Natural Science Foundation of Shandong Provincial of China(Grant No.ZR2020ZD04)+2 种基金Hunan Provincial Key R&D Plan of China(Grant No.2021GK2009)Shenzhen Science and Technology Plan of China(Grant No.JCYJ20180508151903646)Hunan Provincial Innovation Platform and Talent Plan of China(Grant No.2022RC3033).
文摘An Al-Mg-Sc-Zr alloy was additively manufactured by laser direct energy deposition(DED)under different laser powers,and the microstructures and mechanical properties of the as-deposited samples were investigated.The samples showed a fully equiaxed grain structure with grain sizes of 2–30μm.Most of the blocky primary Al3(Sc,Zr)-precipitated phases(<5μm)were arranged along the grain boundaries.A small amount of fine granular secondary Al3(Sc,Zr)phases(<0.5μm)were precipitated owing to the cyclic heat treatment during the DED forming process.According to the EBSD(Electron backscatter diffraction)results,the texture index and strength of the sample were only slightly greater than 1,indicating that the material structure exhibited a certain but not obvious anisotropy.The sample in the horizontal direction had better yield strength,tensile strength,and elogation properties(399.87 MPa,220.96 MPa,9.13%)than that in the building direction(385.40 MPa,219.40 MPa,8.24%),although the sample in the〈XOZ〉plane had the finest equiaxed grains.The ductility of the〈XOZ〉sample deteriorated as the number of pores increased.
基金supported by the National Key Re-search and Development Program of China(2021YFB3700904)the National Natural Science Foundation of China(No.U21B2073)the Hunan Innovation Platform and Talent Plan under Grant(No.2022RC3033).
文摘Hydrogen pores in laser additive manufacturing(LAM)aluminum alloys have long been a major challenge for its application.In this study,the formation mechanisms of hydrogen pores and its kinetic behaviors were systematically investigated in laser directed energy deposited(L-DED)AlMgScZr alloy.The results indicated that hydrogen pores accumulated layer by layer at the melt pool boundaries,due to the high nucleation rate and insufficient time to escape of hydrogen pores at the melt pool boundaries.Dring the AlMgScZr powder at 150°C/4 h enabled the significant decrease of moisture content from 0.0520 wt%to 0.0096 wt%,while the porosity of the L-DED sample only decreased from 0.51%to 0.36%.The increase of laser power decreased the porosity of L-DED sample.Except the L-DED parameters,the alloy composition exerted a more significant influence on hydrogen porosity.When the Mg content increased from 9 wt%to 14 wt%,the porosity exhibited an increase from 0.36%to 0.52%.Conversely,the incorporation and subsequent augmentation of Si content resulted in a significant reduction in porosity,reaching as low as 0.15%with an increase to 2 wt%.The solubility and diffusion coefficient of[H]in Al-Mg-Sc-Zr melt with different Mg and Si contents were calculated by density functional theory(DFT).It was observed that increasing the Si content led to a decrease in the nucleation zone for hydrogen pores and reduced poros-ity.A comprehensive porosity inhibition strategy that combines powder drying,process optimization,and composition regulation have been developed.
