1. Beijing Laboratory of Metallic Materials and Processing for Modern Transportation, Beijing100083, China 2. State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China
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DOI:
10.7502/j.issn.1674-3962.2016.11.04
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Abstract:
Cu-based shape memory alloys (Cu-SMAs) have the broadest application prospect owing to their excellent shape memory properties, high electrical and thermal conductivities, wide adjustable range of transformation temperature, as well as low cost. However, the ordinary polycrystalline Cu-SMAs show poor ductility and fatigue life because of suffering from intergranular fracture and low transformation critical stress, which are serious obstacles to wide application of the Cu-SMAs. Fortunately, these issues could be solved well by structure design. This paper reviewed the major progress in structure design of the Cu-based SMAs with high superelasticity and high transformation critical stress in the recent years. The results indicate that according to some principles such as obtaining grain orientation with high phase transformation strain, increasing grain size, obtaining straight low-energy GBs, etc., high superelasticity of above 7% can be obtained in columnar-gained or bamboo-liked-grained Cu-SMAs. Then, high superelasticity of above 5% and high transformation critical stress of above 650MPa can be obtained through reasonable heat treatments.