Instrumented indentation of transforming and no-transforming phases in Cu–Al–Be shape-memory alloys

The behavior of Cu–Al–Be alloys under instrumented indentation using a Berkovich tip was studied. The pseudoelastic effect was evidenced in the transforming β Cu–Al–Be phase as a closed hysteresis loop between the unloading–reloading paths in the P–h curves and high depth recovery ratios. From series of indentations conducted in the (β + γ2) specimens, it was found that the indentation response of the two phases is remarkably different. Unlike the pseudoelastic β phase, γ2 precipitates present an elastic–plastic behavior, obtaining a complete coincidence between the unload and reload path in the load–displacement curves, and a lower recovery capacity. An average contact pressure versus the penetration depth curve was estimated for each indentation curve, and results suggest that 8 GPa and 3 GPa can be considered an elastic limit for γ2 and β phase respectively under Berkovich indenter stress state. The elastic modulus and the hardness of both phases were estimated from load–displacement curves using the Oliver and Pharr method.