期刊
MATERIALS CHARACTERIZATION
卷 178, 期 -, 页码 -出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/j.matchar.2021.111273
关键词
Shape memory alloy; NiTi alloy; Severe plastic deformation; Microstructure; Martensite twin; Mechanical property
类别
资金
- National Natural Science Foundation of China [51475101, 51871070]
B2 austenite NiTi shape memory alloy can undergo severe plastic deformation and annealing to form nanostructured NiTi SMA with unique martensite twin structures. The stress-induced martensite transformation of NiTi SMA is related to grain size, with nanostructured NiTi SMA possessing higher yield stress compared to solution-treated NiTi SMA. Grain refinement plays a significant role in enhancing the yield stress of NiTi samples.
B2 austenite NiTi shape memory alloy (SMA) with the chemical composition of Ni-49.3 at.%Ti underwent severe plastic deformation and subsequent annealing at 450 degrees C for various times, including 4, 8 and 12 h. As a result, { } nanostructured NiTi SMA can be obtained by crystallization of amorphous NiTi SMA. In particular, 111 type I martensite twin and {111} type I martensite twin are found to appear in nanostructured NiTi samples where B2 austenite is dominant in the matrix. Compared to the solution-treated NiTi SMA, nanostructured NiTi SMA possesses an extremely high yield stress. The effect of grain refinement plays a pronounced role in enhancing yield stress of NiTi sample. In addition, the critical stress for inducing martensite transformation decreases with the increase of grain size. This means that stress-induced martensite transformation of NiTi SMA is related to grain size and it is gradually inhibited with decreasing nanocrystalline grain size.
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