摘要
The mechanisms responsible for deformation behavior in Nb/NiTi composite during pre-straining were investigated systematically using in-situ synchrotron X-ray diffraction, transmission electron microscopy and tensile test. It is shown that upon loading, the composite experiences elastic elongation and slight plastic deformation of B19′,B2 and β-Nb phases, together with the forward stress-induced martensitic(SIM) transformation from B2 to B19′. Upon unloading, the deformation mechanisms of the composite mainly involve elastic recovery of B19′, B2 and β-Nb phases,compression deformation of β-Nb phase and incomplete B19′→B2 reverse SIM transformation. In the tensile loading-unloading procedure, besides the inherent elastic deformation and SIM transformation, the(001) compound twins in B19′ martensite can also be conducive to the elastic deformation occurring in B19′-phase of the composite.Therefore, this composite can exhibit a large recoverable strain after unloading owing to the elastic deformation, and the partially reversible and consecutive SIM transformation together with the(001) compound twins.
通过原位同步辐射X射线衍射、透射电子显微术和拉伸测试等表征手段,系统研究Nb/NiTi复合材料在预变形过程中的变形机制。结果表明:在加载过程中,Nb/NiTi复合材料经历B19′、B2和β-Nb相的弹性伸长和轻微的塑性变形,以及从B2相到B19′相的应力诱发马氏体相变。在随后的卸载过程中,Nb/NiTi复合材料的变形机制主要包括B19′、B2和β-Nb相的弹性恢复,β-Nb相的压缩变形以及不完全B19′→B2逆马氏体相变。在拉伸加载-卸载过程中,除了固有的弹性变形和应力诱发马氏体相变以外,复合材料中B19′马氏体内部的(001)复合孪晶也有助于材料实现弹性变形。因此,由于弹性变形、部分可逆且“连续”的应力诱发马氏体相变以及(001)复合孪晶的共同作用,Nb/NiTi复合材料在卸载完成后能够呈现出大的可恢复应变量。
基金
the National Natural Science Foundation of China (Nos.51771082,51971009,52175410,51801076)
the Six Talent Peaks Project in Jiangsu Province,China (No.2019-XCL-113)
Zhenjiang Science & Technology Program,China (No.GY2020001)
Project of Faculty of Agricultural Equipment of Jiangsu University,China (No.NZXB20200101)
the US Department of Energy,Office of Science and Office of Basic Energy Science (No.DE-AC02-06CH11357) for providing the Advanced Photon Source。
