A shape memory gold alloy processed by rapid solidification

In the ternary system Au–Cu–Al, the β phase has a displacive transformation which can be tailored for a shape memory effect. The sequence of allotropic transformations of the β phase as a function of temperature and cooling conditions is reported in this work. The structure of the martensite (monoclinic) and the type of parent phase are identified. Rapid solidification is employed as a tool for freezing the high temperature modification and compared to quenching from the solid state. DSC analyses clearly demonstrate the thermodynamic order of transformations and the temperatures of the forward and reverse martensitic transformation. A transformation from metastable B2 to L21 has been revealed for the first time. The transformation is endothermic and irreversible.The thin ribbon sample has been used to show the one-way shape memory effect.