Stress-induced martensitic transformation in nanometric NiTi shape memory alloy strips: An in situ TEM study of the thickness/size effect
Stress-induced martensitic transformation in nanometric NiTi shape memory alloy strips: An in situ TEM study of the thickness/size effect
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纳米 NiTi 形状记忆合金带材中应力诱发的马氏体转变：厚度/尺寸效应的原位 TEM 研究
DOI：
10.1016/j.jallcom.2013.05.054
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发表时间：
2013-12-05
影响因子：
6.2
通讯作者：
Han, X. D.
中科院分区：
文献类型：
--
作者：
Mao, S. C.;Li, H. X.;Han, X. D.
通过聚焦离子束铣削多晶 NiTi 形状记忆合金制造了厚度为 40-83 nm 的超薄 NiTi 微型带材。使用自行设计的拉伸装置在透射电子显微镜内对镍钛带材进行拉伸变形，以原位检查厚度对带材中应力诱导马氏体相变行为的影响。研究表明，这种转变在厚度为 40 nm 的条带中被完全抑制，而在更厚的条带中则可能发生这种转变。在这些带材中，发现应力诱发的马氏体转变首先在较厚的带材中开始，然后在较高应变（应力）水平下在较薄的带材中开始，这证明了尺寸效应。这种尺寸效应归因于表面损坏的影响，包括带材一侧的 Ga+ 浸渍非晶层，这是由使用 FIB 制造样品造成的，以及两侧的氧化影响层。这意味着观察到的“尺寸效应”不是 NiTi 马氏体相变的内在行为，而是外部影响的结果。(C) 2013 Elsevier B.V. 保留所有权利。
Ultrathin NiTi miniature strips of 40-83 nm in thickness were fabricated by means of focused ion beam milling from a polycrystalline NiTi shape memory alloy. The NiTi strips were subjected to tensile deformation inside a transmission electron microscope using a self-designed tension apparatus for in situ examination of the effect of thickness on the stress induced martensitic transformation behavior in the strips. The study revealed that the transformation was completely suppressed in a strip of 40 nm in thickness whereas it was possible in thicker strips. In these strips, the stress induced martensitic transformation was found to commence sequentially in thicker strips first and then in thinner strips at higher strain (stress) levels, demonstrating the size effect. This size effect is attributed to the effect of damaged surfaces, including a Ga+-impregnated amorphous layer on one side of the strip caused by sample fabrication using FIB and oxidation affected layers on both sides. This means that the observed "size effect'' is not an intrinsic behavior of the martensitic transformation in NiTi but of extrinsic influences. (C) 2013 Elsevier B.V. All rights reserved.