Design Principle of Long-Life Shape Memory Alloy Based on the Geometry of Martensite Microstructure

Abstract

In order to establish a principle for suppressing the functional fatigue of shape memory alloys, we are investigating the geometrical condition of the martensite microstructure consisting only of the compatible interfaces, and the relationship between deviation from the geometric condition and the functional fatigue. We give an overview of the previous researches on how to understand the martensite microstructure based on the geometry of deformation, and the basic concepts to suppress the accumulation of dislocations upon cyclic actuation of shape memory alloys. Finally, we introduce the Triplet Condition (TC), a new condition of supercompatibility between martensitic variants, formulated by the authors and discuss the potential of TC for a design principle of durable shape memory alloy.