The Mechanism of Rubber-Like Behavior in Cu-Zn-Al Martensite
Dept. of Applied Physics, Hokkaido University, Sapporo 060, Japan
Martensites in several shape memory alloys have been found to exhibit the rubber-like behavior since its discovery in a Au-Cd alloy by Ölander. However, the detailed mechanism of this behavior, particularly, the origin of the restoring force has not been clarified yet. In the present paper, following a brief review of experimental results obtained for a Cu-Zn-Al alloy , a new model proposed recently to explain the rubber effect is presented. In the model, it is assumed that the SRO structure develops during aging in martensites. The variant reorientation disturbs the once developed SRO structure, leading to an increase in the configurational part of the free energy. The equilibrium SRO parameter in the martensite at room temperature was calculated using the cluster variation method, and the restoring force was estimated. The results are consistent with the experiments.
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