Transformation Volume Effects on Shape Memory Alloys

Abstract

It is generally accepted that the martensitic transformations (MTs) in the shape memory alloys (SMAs) are mainly characterized by the shear deformation of the crystal lattice that arises in the course of MT, while a comparatively small volume change during MT is considered as the secondary effect, which can be disregarded when the basic characteristics of MTs and functional properties of SMAs are analyzed. This point of view is a subject to change nowadays due to the new experimental and theoretical findings. The present article elucidates (i) the newly observed physical phenomena in different SMAs in their relation to the volume effect of MT; (ii) the theoretical analysis of the aforementioned volume-related phenomena.

Keywords

• shape memory alloy
• volume change
• elastic modulus
• crystal defects
• martensite stabilization
• entropy change