Changes of shape memory properties in CuAlNi single crystals subjected to isothermal treatments

Abstract

CuAlNi shape memory alloys are candidates for high temperature applications, mainly for their low diffusion at temperatures higher than room temperature. Aging thermal treatments made to the β-CuAlNi single crystal phase at 423 K were conducted in order to study how the main properties of these alloys change. Aging of the metastable β-phase above room temperature but well below the eutectoid point can favor a further ordering process started during quenching and trigger the decomposition of part of the alloy into more stable phases. Changes on the thermally and stress induced martensitic transformations were observed after these aging treatments, modifying the thermal and mechanical response of the material. Modifications of the metastable phase transformation diagrams are considered as well as the pseudoelastic fatigue behavior of the alloys.