Grain size and pseudoelastic behaviour of a Cu–Al–Be alloy

The effect of grain size on the pseudoelastic behaviour of a Cu-11.4 wt.% Al-0.5 wt.% Be shape memory alloy was studied. Annealing at 1073 K leads to grain growth with a kinetic exponent around 0.5. The martensite-start stress (σs), the pseudoelastic slope and the stress hysteresis decrease as the grain size increases. The effect of grain constraint on σs for CuAlBe is stronger than for other shape memory alloys but it is very weak on the pseudoelastic behaviour. Pseudoelastic cycling with increasing strain beyond 2% leads to a decrease in σs and an increase in the strain retained on unloading, due to increasing retention of the martensite phase on unloading. The important overheating needed for the transformation to β phase indicates that the stress-induced martensite is effectively stabilized.