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 (σ_y), the work-hardening rate after yielding (dσ_PE/dε) and the stress hysteresis (Δσ) in the wires with a random texture decrease with increasing d/D. The transformation strain (ε_TS) and the maximum pseudoelastic strain (εPEMAX) 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 σ_y, dσ_PE/dε and Δσ increase proportionally with increasing (1 - (d/D))² while the ε_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 σ_y and the ε_TS for wires with a 〈1 1 0〉 fiber texture are larger and smaller than those for wires with a random texture, respectively.