J. Li, China university of Petroleum,Beijing, Beijing, China; Y. Zheng, L. Cui, China University of Petroleum, Beijing, China
An incomplete transformation cycle induces a kinetic stop in the following complete transformation cycle in shape memory alloys. Therefore, the kinetic stop can be regarded as a memory of the previous arrest temperature. Herein, we show that the temperature memory effect of a TiNi shape memory alloy can be expanded to be operational in a very wide temperature range by designing the shape of the original surface curve and cold rolling, which may be exploited for various practical applications.
Summary: The martensitic transformation and associated thermal expansion behaviors of a NiTi alloy were studied in this paper. Cold deformations higher than the recoverable limit cause massive dislocations in the NiTi alloy. By controlling the ratio of the cold deformation, the density of dislocations can be managed, and therefore the thermal-mechanical behaviors of the NiTi alloy can be tailored due to the interactions between the martensite variants and the dislocation texture. Due to the interactions between the domains with different dislocation density, the reverse transformation expands over a large temperature window. This is quite useful to output strains in a large temperature window comprising to conventional SMA composites interface which will be failure in the same temperature.
