Ti-Ta-Zr合金薄膜的马氏体相变与形状记忆效应

Ti-Ta alloy is a kind of promising high temperature shape memory alloy (SMA) due to its excellent plasticity and high transformation temperature. However, its decrease of transformation temperature during thermal cycles seriously prohibits its further development and applications. In the present project, a Ti-Ta-Zr SMA thin films is obtained by Zr doping to improve the thermal stability and shape memory effect. The Ti-Ta-Zr thin films are fabricated by the magnetron sputtering technique. The influence rules of Zr content on microstructure, martensitic transformation and its stability, mechanical behavior and shape memory effect of Ti-Ta-Zr thin films are investigated. The evolution of structure during the thermal cycles is investigated to disclose the mechanism of Zr addition influence on thermal stability. The effect of Zr content on the evolution of microstructure during martensitic deformation and reserve martensitic transformation are investigated to disclose the mechanism of Zr addition improving of shape memory effect. The relationship among Zr content, martensitic transformation and its stability, reversible strain is built up. The most suitable Zr content to achieve the high transformation temperature stability and large recovery strain is found. The Ti-Ta-Zr high-temperature SMA thin film with high stability and good shape memory effect is developed.

Ti-Ta合金塑性好、相变温度高，是一种极具潜力的高温记忆合金，但Ti-Ta合金在热循环过程中相变温度下降，已成为制约其发展和应用的瓶颈。本项目拟采用Zr掺杂提高Ti-Ta合金薄膜热稳定性，改善形状记忆效应。采用磁控溅射制备Ti-Ta-Zr高温记忆合金薄膜；研究Zr含量对微观组织结构、马氏体相变及其稳定性、力学行为和形状记忆效应的影响规律；阐明热循环过程中的组织结构演化规律，揭示Zr掺杂对热稳定性影响的物理本质；阐明Zr含量对马氏体变形及其逆相变过程中微观组织结构演化规律的影响，揭示Zr掺杂改善形状记忆效应的微观机制，建立Zr含量、马氏体相变温度及其稳定性、可逆应变量之间的内在联系，确定具有高相变温度稳定性和大可逆应变的最佳Zr含量，制备出高稳定性、良好形状记忆效应的Ti-Ta-Zr高温记忆合金薄膜。

记忆合金薄膜集温度、应力感知和驱动为一体，比表面积小、输出功率大，且兼具体材料的各种优点，在微机电领域有广阔的应用前景。传统TiNi合金可恢复应变高，但由于其相变温度低，限制了其在高温环境中的应用。Ti-Ta合金塑性好、相变温度高，是一种极具潜力的高温记忆合金，但Ti-Ta合金形状记忆效应不足。本项目采用磁控溅射方法制备了Ti-Ta-Zr基记忆合金薄膜，优化了薄膜制备工艺参数，获得了高质量的记忆合金薄膜。系统研究了Ti-Ta-Zr基合金薄膜的组织结构、马氏体相变、力学性能和形状记忆效应。研究了Ti-18.5Ta-8.5Zr合金薄膜晶粒尺寸对形状记忆效应的影响规律，当晶粒尺寸为10nm时，回复率为65%；当晶粒尺寸为8nm时，形状记忆效应消失。Ti-15Ta-15Zr-1Fe合金薄膜室温下为α″马氏体，As为145℃，抗拉强度为657MPa，断裂延伸率为12.%，并具有双程记忆效应。这些研究成果为高温记忆合金薄膜应用提供了理论基础。