Grain size dependence of pseudoelasticity in polycrystalline Cu-Al-Mn-based shape memory sheets

The effects of grain size on the stress strain characteristics of Cu-Al-Mn-based pseudoelastic (PE) sheet specimens with various relative grain sizes d/t (d = grain size, t = sheet thickness) were investigated using cyclic tensile testing. The stress strain characteristics such as the yield stress sigma(y), work-hardening rate d sigma(PE)-/d epsilon and stress hysteresis of pseudoelasticity Delta sigma decreased, and the obtained maximum PE strain sigma(MAX)(PE) with increasing d/t. The sigma(y), d sigma(PE)/d epsilon, Delta sigma and epsilon(MAX)(PE) plots as a function of d/t were divided into three regions. The critical points dividing the plots into the three regions were located at d/t approximate to 1 and d/t approximate to 2. These results can be explained from the standpoint of constraints between grains, depending on grain structure such as a fine equiaxed grain structure, a columnar-like grain structure and a fully columnar grain structure. (c) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.