圧延と焼なましが Fe-Mn-Si 形状記憶合金の形状記憶特性に及ぼす影響

抄録

The shape memory effect (SME) in Fe-Mn-Si based alloy is associated with γ ⇄ ε martensitic transformation. It is necessary to suppress the sliding deformation and promote preferential generation of the martensitic transformation in order to improve the SME. In this study, each specimen was rolled and/or annealed and then the elastic and shape recovery ratios of them were checked by means of the bending mechanical test. Crystal structures also were inspected by electron backscatter diffraction (EBSD) for obtaining the phase distribution maps and then pole figures were drawn. On the specimens rolled as 20% and 40% reduction rate the axis of some crystals oriented to one of [001], [2 0 1], [ 1], [ 1] and the other of [001], [0 1], [ 1], [ 1]. The elastic recovery ratio improved from 27% to 36% at the reduction ratio (RR) at 20% , and to 40% at the RR 40% , however the shape recovery ratio was not improved. After the 600℃ annealing the shape recovery ratio improved from 20% to 33% in the RR 40% specimens. The cause of the elastic recovery ratio improvement is presumed that the cold rolling raised yield stress, and the expansion of martensite phase after bending test enhanced pseudoelastic effect. On the other hand, there are two reasons for improving the SME, one is the texture formation which promotes the martensitic transformation, and the other is the generation of austenite phase which easily transforms into martensite phase.