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)MAX PE) increase with increasing d/D. The effect of grain size on pseudoelastic behaviors can be clarified from the 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 (left angle bracket)1 1 0(right angle bracket)fiber texture are larger and smaller than those for wires with a random texture, respectively.