FeMnSi基形状記憶合金薄板の二軸引張変形に対する形状回復特性

Abstract

FeMnSi-based shape memory alloy (SMA) has already been used practically as steel pipe joints. In most cases of the applications, it is possible to estimate the reduction of diameter from the present data measured on the shape recovery for a uniaxial stretch of FeMnSi-based SMA. However, to promote the extensive practical application of FeMnSi-based SMA, investigations of shape recovery characteristics for biaxial stretch are significant. In this study, shape recovery characteristics for uniaxial tensile stretch, biaxial tensile stretch, and the stretch of the transition field from simple tension to biaxial tension are investigated. In addition, microstructures of FeMnSi-based SMA are observed, and the mechanism of stress-induced martensitic transformation which controls shape recovery actions is interpreted. Shape recovery strain after biaxial tensile stretch is markedly smaller than that of simple tensile stretch. The relationship of shape recovery characteristics to orientations of the ε-phase is clarified from microstructural observations. The technical data and interpretation presented in this study should be useful in forming design guidelines for promoting the extensive application of FeMnSi-based SMA.