Degradation of Transformation Stress in a Bicrystal Cu-Al-Mn Shape-Memory Alloy Using Full-Field Stress and Strain Measurements

Abstract

The functional fatigue behavior of the superelasticity of a bicrystal Cu-Al-Mn shape-memory alloy during compressive cycles is investigated using the combined techniques of digital image correlation and data-driven identification. The evolution of the inhomogeneous distribution of the transformation stress and strain fields with the number of cycles within two grains with different orientations is investigated. It is found that the transformation stress of the bottom grain is higher than that of the top grain. Furthermore, the transformation stress degrades faster in the bottom grain during cyclic deformation. The decrease in transformation stress in the bottom grain first occurs near the grain boundary and then propagates towards the lower part of the bottom grain. The correlations between the martensitic transformation, accumulation of irrecoverable strain, and degradation of transformation stress are discussed, giving the functional fatigue of bicrystal Cu-Al-Mn shape-memory alloys.