Xue Deqing, Yuan Ruihao, Zhou Yumei, Xue Dezhen, Lookman Turab, Zhang Guojun, Ding Xiangdong, Sun Jun
State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China.
School of Materials Science and Engineering, Xi'an University of Technology, Xi'an 710048, China.
Sci Rep. 2016 Jun 22;6:28244. doi: 10.1038/srep28244.
The large thermal hysteresis (ΔT) during the temperature induced martensitic transformation is a major obstacle to the functional stability of shape memory alloys (SMAs), especially for high temperature applications. We propose a design strategy for finding SMAs with small thermal hysteresis. That is, a small ΔT can be achieved in the compositional crossover region between two different martensitic transformations with opposite positive and negative changes in electrical resistance at the transformation temperature. We demonstrate this for a high temperature ternary Ti-Pd-Cr SMA by achieving both a small ΔT and high transformation temperature. We propose two possible underlying physics governing the reduction in ΔT. One is that the interfacial strain is accommodated at the austenite/martensite interface via coexistence of B19 and 9R martensites. The other is that one of transformation eigenvalues equal to 1, i.e., λ2 = 1, indicating a perfect coherent interface between austenite and martensite. Our results are not limited to Ti-Pd-Cr SMAs but potentially provide a strategy for searching for SMAs with small thermal hysteresis.
温度诱导马氏体相变过程中的大热滞（ΔT）是形状记忆合金（SMA）功能稳定性的主要障碍，特别是在高温应用中。我们提出了一种寻找具有小热滞的形状记忆合金的设计策略。也就是说，在两种不同马氏体相变的成分交叉区域可以实现小的ΔT，这两种相变在转变温度下具有相反的正、负电阻变化。我们通过实现小的ΔT和高转变温度，在高温三元Ti-Pd-Cr形状记忆合金中证明了这一点。我们提出了两种可能导致ΔT减小的潜在物理机制。一种是通过B19和9R马氏体的共存，在奥氏体/马氏体界面处适应界面应变。另一种是转变特征值之一等于1，即λ2 = 1，这表明奥氏体和马氏体之间存在完美的共格界面。我们的结果不仅限于Ti-Pd-Cr形状记忆合金，还可能为寻找具有小热滞的形状记忆合金提供一种策略。
