Development and Characterization of Ti-Ni-X Ternary Shape Memory Alloy Thin Films

Ti-Ni形状记忆合金薄膜具有制作微致动器的大变形和恢复力等巨大优势，此外，即使是形状记忆合金固有的缺点，例如由于冷却速率的限制而导致的响应慢，也可以在薄膜中得到极大改善。因此，对Ti-Ni形状记忆合金薄膜的研究具有迫切的需求。本课题成功地在溅射沉积的Ti-Ni-Cu和Ti-Ni-Pd三元形状记忆合金薄膜中获得了理想的形状记忆效应。结果表明，合金的相变温度和形状记忆特性受热处理工艺和合金成分的影响较大。Ti-Ni-Cu和Ti-Ni-Pd三元形状记忆合金薄膜分别表现出小的温度滞后和高的相变温度，这些特性有效地实现了高响应的致动器特性。Ti-Ni-Pd薄膜在冷却和加热时表现出与Ti-Ni二元合金薄膜相似的单阶段相变。相应地，它们在冷却和加热时都表现出单阶段变形。Ti-Ni-Cu薄膜表现出两个阶段的转变，因此两个阶段的变形;第一阶段对应于B2和O（正交）相之间的转变和0-和M-相之间的第二阶段。第一阶段的转变伴随着一个小的温度滞后。这些薄膜均表现出良好的形状记忆效应。

Ti-Ni shape memory alloy thin films have great advantages such as large deformation and recovery force for fabricating microactuators ; besides, even an intrinsic disadvantage of the shape memory alloy such as a slow response due to the limitation of cooling rate can be greatly improved in thin films. Therefore, the development of Ti-Ni shape memory alloy thin films has been keenly demanded. The present project has been successful in developing a perfect shape memory effect in sputter-deposited Ti-Ni-Cu and Ti-Ni-Pd ternary shape memory alloy thin films were also made by sputtering. They showed a small temperature hysteresis and high transfo, The transformation temperatures and shape memory characteristics were found to be strongly affected by heat-treatment and alloy composition. Ti-Ni-Cu and Ti-Ni-Pd ternaryshape memory alloy thin films showed a small temperature hysteresis and high transformation temperatures, respectively ; these characteristics are effective to achieve a high response actuator characteristic. The Ti-Ni-Pd thin film showed a single stage transformation upon cooling and heating similarly to a Ti-Ni binary alloy thin films. Corre- sponding, they showed a single stage deformation both upon cooling and heating. The Ti-Ni-Cu thin film showed a two-stage transformation and hence a two-stage deformation ; the first stage corresponds to the transformation between B2 and O(Orthorhombic)-phase and the second stage between the 0- and M-phases. The first stage transformation was accompanied by a small temperature hysteresis. All these thin films showed perfect shape memory effect.