Effect of grain size and texture on pseudoelasticity in Cu-Al-Mn-based shape memory wire

The effect of the relative grain size d/D (d. grain size, D: wire diameter) on stress-strain characteristics was investigated in Cu-Al-Mn-based shape memory alloy (SMA) wires. The yield stress (sigma(y)), the work-hardening rate after yielding (d sigma(PE)/d epsilon) and the stress hysteresis (Delta sigma) in the wires with a random texture decrease with increasing d/D. The transformation strain (epsilon(TS)) and the maximum pseudoelastic strain (epsilon(PE)(MAX)) increase with increasing d/D. The effect of grain size on pseudoelastic behaviors can be clarified from the PE volume fraction of three-dimensionally constrained grains and the sigma(y), d sigma(PE)/d epsilon and Delta sigma increase proportionally with increasing (1-(d/D))(2) while the epsilon(TS) decreases proportionally with increasing (1-(d/D))(2). Consequently, the effect of grain size on the pseudoelastic behaviors can be expressed using the Taylor and inverse Schmid factors. The sigma(y) and the epsilon(TS) for wires with a < 110 > fiber texture are larger and smaller than those for wires with a random texture, respectively. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.