Effect of solution treatment on the microstructure,phase transformation behavior and functional properties of NiTiNb ternary shape memory alloys fabricated via laser powder bed fusion in-situ alloying  

作　　者：Rui Xi Hao Jiang Guichuan Li Zhihui Zhang Huiliang Wei Guoqun Zhao Jan Van Humbeeck Xiebin Wang 

机构地区：[1]Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials(Ministry of Education),Shandong University,Jingshi Road 17923,Jinan 250061,People's Republic of China [2]Department of Materials Engineering,University of Leuven(KU Leuven),Kasteelpark Arenberg 44 bus 2450,Heverlee B3001,Belgium [3]Key Laboratory of Bionic Engineering(Ministry of Education),Jilin University,Renmin Street 5988,Changchun 130025,People's Republic of China [4]School of Mechanical Engineering,Nanjing University of Science and Technology,Xiaolingwei Street 200,Nanjing 210094,People's Republic of China

出　　处：《International Journal of Extreme Manufacturing》2024年第4期202-223,共22页极端制造（英文）

基　　金：supported by the Natural Science Foundation of Shandong Province (ZR2020YQ39, ZR2020ZD05);Taishan Scholar Foundation of Shandong Province (tsqn202211002);the Young Scholars Program of Shandong University (Grant Number 2018WLJH24)

摘　　要：Post-heat treatment is commonly employed to improve the microstructural homogeneity and enhance the mechanical performances of the additively manufactured metallic materials.In this work,a ternary(NiTi)91Nb9(at.%)shape memory alloy was produced by laser powder bed fusion(L-PBF)using pre-alloyed NiTi and elemental Nb powders.The effect of solution treatment on the microstructure,phase transformation behavior and mechanical/functional performances was investigated.The in-situ alloyed(NiTi)91Nb9 alloy exhibits a submicron cellular-dendritic structure surrounding the supersaturated B2-NiTi matrix.Upon high-temperature(1273 K)solution treatment,Nb-rich precipitates were precipitated from the supersaturated matrix.The fragmentation and spheroidization of the NiTi/Nb eutectics occurred during solution treatment,leading to a morphological transition from mesh-like into rod-like and sphere-like.Coarsening of theβ-Nb phases occurred with increasing holding time.The martensite transformation temperature increases after solution treatment,mainly attributed to:(i)reduced lattice distortion due to the Nb expulsion from the supersaturated B2-NiTi,and(ii)the Ti expulsion from theβ-Nb phases that lowers the ratio Ni/Ti in the B2-NiTi matrix,which resulted from the microstructure changes from non-equilibrium to equilibrium state.The thermal hysteresis of the solutionized alloys is around 145 K after 20%pre-deformation,which is comparable to the conventional NiTiNb alloys.A short-term solution treatment(i.e.at 1273 K for 30 min)enhances the ductility and strength of the as-printed specimen,with the increase of fracture stress from(613±19)MPa to(781±20)MPa and the increase of fracture strain from(7.6±0.1)%to(9.5±0.4)%.Both the as-printed and solutionized samples exhibit good tensile shape memory effects with recovery rates>90%.This work suggests that post-process heat treatment is essential to optimize the microstructure and improve the mechanical performances of the L-PBF in-situ alloyed parts.

关 键 词：shape memory alloy NiTiNb laser powder bed fusion in-situ alloying heat treatment 

分 类 号：TG139.6[一般工业技术—材料科学与工程] TG156.94[金属学及工艺—合金]