Formation mechanism of inherent spatial heterogeneity of microstructure and mechanical properties of NiTi SMA prepared by laser directed energy deposition  

作　　者：MengJie Luo Ruidi Li Dan Zheng JingTao Kang HuiTing Wu ShengHua Deng PengDa Niu 

机构地区：[1]State Key Laboratory of Powder Metallurgy,Central South University,Changsha,Hunan 410083,People’s Republic of China [2]Faculty of Materials Metallurgy and Chemistry,Jiangxi University of Science and Technology,Ganzhou 341000,People’s Republic of China

出　　处：《International Journal of Extreme Manufacturing》2023年第3期548-567,共20页极端制造（英文）

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)。

摘　　要：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.

关 键 词：shape memory alloy gradient functional materials laser directed energy deposition spatial heterogeneity additive manufacturing mechanical properties 

分 类 号：TG139.6[一般工业技术—材料科学与工程]