Evaluation of Thermo-Mechanical Cyclic Properties of Shape Memory Alloy Aiming to Electric Generation System with Mass and Low Temperature Heat Source.

为探讨形状记忆合金作为发电系统能量转换元件的可能性，对形状记忆合金的热-力学循环性能进行了基础研究。本研究使用的SMA合金是在合金稳定性、耐蚀性、相变温度和疲劳性能方面均优于Cu含量为0 ~ 13 at的四种合金的TiNiCu族合金。%。所得结果总结如下：1。马氏体相变温度Ms随Cu含量的增加而升高，反相变温度As随Cu含量的增加而降低，并在高应变范围内达到饱和。在最大应变epsilon_<max>*3%范围内，应变循环的有效应变能w ^<av>随Cu含量的增加而增加，在高应变范围内趋于饱和。分散应变能随Cu含量的增加而降低，即每1个循环中恢复应变能的降低。恢复应变能确定为循环应力-应变迟滞回路的面积。尽管形状记忆热处理温度不同，恢复应变能与疲劳寿命在epsilon_<max>*3%范围内呈直线关系。在最大应变和热处理温度的实验条件下，用对数-对数图评价了弥散应变能与疲劳寿命之间的直线关系。超弹性循环条件下，Cu含量在5 ~ 10%范围内的疲劳寿命较低。另一方面，随着Cu含量的增加，热-机械耦合状态下的疲劳寿命降低。

The basical study of the evaluation of thermo-mechnaical cyclic properties of shape memory alloy (SMA) were performed in order to investigate a possibility to apply of SMA as the energy conversion elements for the electric generation system. The SMA's used in this study were TiNiCu group alloy which had superior properties in the alloy stability, the corrosion resistance, the transformaton temperature and the fatigue property arid four kinds of alloys with Cu contents of 0-13 at.% . The results obtained were summarized as the followings.1. The martensitic transformation temperature Ms increased with increasing of the Cu contents, and the inversed transformation temperature As decreased with the Cu contents and saturated at the high strain range.2. The effective strain energy-W^<av> by strain cycling increased with the Cu contents in the range of the maximum strain epsilon_<max>*3%, and saturated to constant in the high strain range.3. The dispersion strain energy which were determined as the decrease in the recovery strain energy per 1 cycle, decreased with the Cu contents. The recovery strain enrgy was determined as the area of cyclic stress - strain hysteresis loop.4. The relationship between the recovery strain energy and the fatigue life was a straight line in log -log diagram in the range of epsilon_<max>*3% in spite of the defference of shape memory heat treatment temperature.5. The relationship between the dispersion strain energy and the fatigue life was evaluated as a straight line in log - log diagram in the experimental conditions of the maximum strain and the heat treatment temperature in this study.6. The fatigue life in the condition of the super elasticity cycles showed low life in the range of the Cu contents of 5-10%. On the other hand, the fatigue life in the condition of the thermo-mechnaical cucles decreased with the Cu contents.