Microstructure and shape memory behaviour of annealed Ti 51.5 Ni (48.5- x ) Cu x ( x   =  6.5–20.9) thin films

作者：Akira Ishida, Morio Sato · 发表于：The Philosophical Magazine A Journal of Theoretical Experimental and Applied Physics · 年份：2007 · DOI：10.1080/14786430701654394 · 被引用次数：49 · 研究领域：Shape Memory Alloy Transformations、Silk-based biomaterials and applications、Metallic Glasses and Amorphous Alloys

Ti-rich Ti–Ni–Cu amorphous films (Ti51.9Ni41.6Cu6.5, Ti51.6Ni36.8Cu11.6, Ti51.5Ni33.1Cu15.4 and Ti51.7Ni27.4Cu20.9), formed by sputtering, were annealed at 773, 873 and 973 K for 1 h and their structures and shape memory behaviours investigated. All the films annealed at 773 K for 1 h exhibited Guinier–Preston (GP) zones, but these precipitates were absent after annealing at 873 K or higher. Instead of GP zones, coherent plate precipitates of a Ti2Cu phase were formed in films annealed at 873 K for 1 h, when the Cu content was between 11.6 to 20.9 at.%. The strain–temperature curves under constant stresses of Ti51.6Ni36.8Cu11.6 and Ti51.5Ni33.1Cu15.4 films showed a two-step deformation associated with the B2 ↔ B19 ↔ B19′ transformation, whereas Ti51.9Ni41.6Cu6.5 and Ti51.7Ni27.4Cu20.9 films showed a single-step deformation associated with the B2↔B19′ and B2↔B19 transformations, respectively. The two kinds of plate precipitates, GP zones and a Ti2Cu phase were found to be effective to increase the critical stress for plastic strain.