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International Journal of Extreme Manufacturing 2023年第3期5卷 548-567页

作者： MengJie Luo Ruidi Li Dan Zheng JingTao Kang HuiTing Wu ShengHua Deng PengDa Niu State Key Laboratory of Powder Metallurgy Central South UniversityChangshaHunan 410083People’s Republic of China Faculty of Materials Metallurgy and Chemistry Jiangxi University of Science and TechnologyGanzhou 341000People’s Republic of China

Ni51Ti49 at.%bulk was additively manufactured by laser-directed energy deposition(DED)to reveal the microstructure evolution,phase distribution,and mechanical *** 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 *** 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 *** 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.

关键词： shape memory alloy gradient functional materials laser directed energy deposition spatial heterogeneity additive manufacturing mechanical properties

Microstructure and room-temperature tensile property of Ti-5.7Al-4.0Sn-3.5Zr-0.4Mo-0.4Si-0.4Nb-1.0Ta-0.05C with near equiaxed β grain fabricated by laser directed energy deposition technique

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Journal of Materials Science & Technology 2022年第6期101卷 308-320页

作者： MengCheng Deng Shang Sui Bo Yao Liang Ma Xin Lin Jing Chen State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Key Laboratory of Metal High Performance Additive Manufacturing and Innovative Design MIIT ChinaNorthwestern Polytechnical UniversityXi’an 710072China

Near-equiaxed β grain was achieved in the near-α Ti60(Ti-5.7Al-4.0Sn-3.5Zr-0.4Mo-0.4Si-0.4Nb-1.0Ta-0.05C) titanium alloy via laser directed energy deposition(LDED). The microstructural evolution along the building direction and the room-temperature tensile properties along the horizontal and vertical directions(building direction) were systematically studied through SEM and OM. EBSD and XRD were utilized to accurately demonstrate the texture of the α and β phases. The results showed that the α phase presented a low texture intensity, which was ascribed to the weak textured β grain with near-equiaxed morphology, since there are Burgers orientation relationships during the β →α transition. In addition, numerical simulation, combined with the CET curve of Ti60 alloy considering the effect of multi-composition,was utilized to elucidate the formation mechanism of the near-equiaxed β grains. Furthermore, according to the solidification theory, we proposed that the solidification temperature range ΔTfwas more accurate than the growth restriction factor Q in predicting the formation tendency of equiaxed β grain in different titanium alloys. Tensile results showed that the horizontal and vertical samples had similar strength,while the former exhibited larger elongation than the latter. The effect of the near-equiaxed β grain and the internal α phase on mechanical properties were revealed at last.

关键词： laser directed energy deposition Near-αtitanium alloy Equiaxedβgrain Room-temperature tensile property

Effect of Cu-Rich Phase Precipitation on the Microstructure and Mechanical Properties of CoCrNiCux Medium-Entropy Alloys Prepared via laser directed energy deposition

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Acta Metallurgica Sinica(English Letters) 2021年第11期34卷 1591-1600页

作者： Yong Xie Zhixin Xia Jixin Hou Jiachao Xu Peng Chen Le Wan Shagang School of Iron and Steel Soochow UniversitySuzhou 215131China School of Mechanical and Electric Engineering Soochow UniversitySuzhou 215131China

CoCrNiCux(x=0.16,0.33,0.75,and 1)without macro-segregation medium-entropy alloys(MEAs)was prepared using laser directed energy deposition(LDED).The microstructure and mechanical properties of CoCrNiCux alloys with increasing Cu content were *** results indicate that a single matrix phase changes into a dual-phase structure and the tensile fracture behaviors convert from brittle to plastic pattern with increasing Cu content in CoCrNiCux *** addition,the tensile strength of CoCrNiCux alloys increased from 148 to 820 MPa,and the ductility increased from 1 to 11%with increasing Cu *** nano-precipitated particles had a mean size of approximately 20 nm in the Cu-rich phase area,and a large number of neatly arranged misfit dislocations were observed at the interface between the two phases due to Cu-rich phase precipitation in the CoCrNiCu *** misfit dislocations hinder the movement of dislocations during tensile deformation,as observed through transmission electron *** allows the CoCrNiCu alloy to reach the largest tensile strength and plasticity,and a new strengthening mechanism was achieved for the CoCrNiCu ***,twins were observed in the matrix phase after tensile ***,the dual-phase structure with different elastic moduli coordinated with each other during the deformation process,significantly improving the plasticity and strength of the CoCrNiCu alloy.

关键词： Medium-entropy alloys Mechanical properties laser directed energy deposition Misfit dislocations Cu-rich phase

Investigation on the Cracking Mechanism of Melt Growth Alumina/Aluminum Titanate Ceramics Prepared by laser directed energy deposition

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Chinese Journal of Mechanical Engineering(Additive Manufacturing Frontiers) 2023年第4期2卷 23-32页

作者： Yunfei Huang Dongjiang Wu Chengxin Li Weijie Lv Guangyi Ma Cong Zhou Fangyong Niu State Key Laboratory of High-performance Precision Manufacturing Dalian University of TechnologyDalian116024China Department of Mechanical and energy Engineering Southern University of Science and TechnologyShenzhen518055China

Oxide melt growth ceramics(OMGCs)exhibit excellent performance and microstructure stability near their melt-ing point and are expected to become a new structural material for long-term stable service in extremely high-temperature water-oxygen *** to its unique advantages of high efficiency,flexible manufac-turing,and near-net shaping,laser directed energy deposition(LDED)has become a promising technology for the rapid preparation of high-performance ***,owing to the limited understanding of the crack-ing mechanism,the severe cracking problem that hinders OMGCs-LDED towards engineering applications has not been ***/aluminum titanate(Al_(2)O_(3)/Al_(x)Ti_(y)O_(z),A/AT)ceramics are prepared using an LDED system and their cracking characteristics are ***,numerical simulations are conducted to reveal the dominant factors and influencing mechanisms of the cracking *** results demonstrate that the cracking nucleation process is mainly controlled by solidification defects,whereas the cracking propagation process is determined primarily by both the microstructure and stress *** study provides a theoretical basis for the development of appropriate cracking suppression methods for OMGCs-LDED.

关键词： Additive manufacturing laser directed energy deposition Composite ceramics Alumina/aluminum titanate Cracking mechanism

Effect of Aging Parameters on Inconel 718 Fabricated by laser directed energy deposition

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Chinese Journal of Mechanical Engineering(Additive Manufacturing Frontiers) 2023年第4期2卷 112-121页

作者： Nataniel Yong Syn Tham Grace Rui Si Tay Bingqing Yao Kaiqiang Wu ZhiLi Dong School of Materials Science and Engineering Nanyang Technological UniversitySingapore639798Singapore Advanced Remanufacturing and Technology Center(ARTC) Agency for ScienceTechnology and Research(A∗STAR)Singapore637143Singapore School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore639798Singapore

Inconel 718 is a nickel-based superalloy of high interest in high temperature applications such as turbine *** be used in such applications,heat treatments are commonly applied to dissolute Laves phase and to achieve𝛾γ′***,conventional heat treatment methods for wrought Inconel 718 may not be suitable for Inconel 718 fabricated by laser directed energy deposition(LDED)due to its unique microstructure formed during the rapid solidification *** has been a lack of investigation in heat treatments for Inconel 718 fabricated by this process,specifically around the impact of aging parameters on this *** this study,the effects of aging parameters were studied by performing seven different heat treatments,including solutionising and aging *** results indicate that for LDED Inconel 718,a high temperature solution treatment of 1100℃for 1 h followed by single aging at 650℃for 20 h achieved a tensile strength and elongation of 1247 MPa and 23%,***,results indicated that even with a shorter aging time of 10 h,γ′phase was found to be of comparable size to the standard double aged treatment.

关键词： Inconel 718 laser directed energy deposition Heat treatment Microstructure Additive manufacturing

Microstructure and Mechanical Properties of an Ultrahigh-strength Titanium alloy Ti-4.5Al-5Mo-5V-6Cr-1Nb Prepared Using laser directed energy deposition and Forging:A Comparative Study

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Chinese Journal of Mechanical Engineering(Additive Manufacturing Frontiers) 2023年第1期2卷 55-66页

作者： Junwei Yang Haibo Tang Peiyuan Wei Hongwei Gao Jiawei Wang Haixin Huo Yanyan Zhu School of Materials Science and Engineering Beihang UniversityBeijing100191China Research Institute for Frontier Science Beihang UniversityBeijing100191China National Engineering Laboratory of Additive Manufacturing for Large Metallic Components Beihang UniversityBeijing100191China Ningbo Institute of Technology Beihang UniversityNingbo315800China

The application of titanium alloys in aerospace put forward the requirement for higher *** manu-facturing is a promising method for the efficient and economical processing of titanium ***,research on the additive manufacturing of ultrahigh-strength titanium alloys is still *** mechanisms of microseg-regation for high alloying elements and poor plasticity are still not *** this study,an ultrahigh-strength titanium alloy Ti-4.5Al-5Mo-5V-6Cr-1Nb(TB18)was prepared using two methods:laser direct energy deposi-tion(LDED)and *** LDEDed alloy contains three zones with similar grain morphologies but different *** microsegregation of the alloy is limited due to the rapid solidification and almost eliminated after the thermal cycle and solution *** stress relief treatment,the LDEDed alloy exhibits anisotropic mechanical *** solution and aging treatments,its ultimate strength is enhanced;however,its plas-ticity is relatively lower than that of the wrought alloy with equally high *** excellent balance of the strength and plasticity of the wrought alloy can be ascribed to the formation of𝛼WGB and multiscale𝛼laths,which provides enlightenment for optimizing the properties of the LDEDed alloy.

关键词： Ultrahigh-strength titanium alloy laser directed energy deposition TB18 Microstructure Tensile properties Heat treatment

Microstructure and mechanical property of additively manufactured NiTi alloys:A comparison between selective laser melting and directed energy deposition

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Journal of Central South University 2021年第4期28卷 1028-1042页

作者： ZHENG Dan LI Rui-di YUAN Tie-chui XIONG Yi SONG Bo WANG Jia-xing SU Ya-dong State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China State Key Laboratory of Materials Processing and Die&Mould Technology Huazhong University of Science and TechnologyWuhan 430074China Shenyang Aircraft Design and Research Institute Shenyang 110035China

NiTi shape memory alloy(SMA)with nominal composition of Ni 50.8 at%and Ti 49.2 at%was additively manufactured(AM)by selective laser melting(SLM)and laser directed energy deposition(DED)for a comparison study,with emphasis on its phase composition,microstructure,mechanical property and deformation *** results show that the yield strength and ductility obtained by SLM are 100 MPa and 8%,respectively,which are remarkably different from DED result with 700 MPa and 2%.The load path of SLM sample presents shape memory effect,corresponding to martensite phase detected by XRD;while the load path of DED presents pseudo-elasticity with austenite *** SLM sample,fine grain and hole provide a uniform deformation during tensile test,resulting in a better ***,the nonequilibrium solidification was studied by a temperature field simulation to understand the difference of the two 3D printing *** temperature gradient G and growth rate R determine the microstructure and phase in the SLM sample and DED sample,which leads to similar grain morphologies because of similar G/*** higher G×R of SLM leads to a finer grain size in SLM sample,providing enough driving force for martensite transition and subsequently changing texture compared to DED sample.

关键词： Ni50.8Ti49.2 shape memory alloy additive manufacturing selective laser melting laser directed energy deposition mechanical properties