An isothermal martensitic transformation in a quenched Au-49.5at%Cd alloy

In the Au-Cd alloy system, two different martensitic transformations are known to date. For Au-47.5at%Cd composition, the {beta}{sub 2}(B2) {yields} {gamma}{sub 2}{prime} (orthorhombic) transformation occurs, while for Au-49.5at%Cd composition the {beta}{sub 2} {yields} {zeta}{sub 2}{prime} (trigonal) transformation. The former transformation is well-known for the first discovery of the shape memory effect and the rubber-like behavior, and as one of the prototypes for which the phenomenological crystallographic theory was successfully applied. On the contrary, the latter transformation was not understood until recently. The crystal structure of the martensite, the shape memory effect, superelasticity and the rubber-like behavior were found only recently. The kinetics of the {beta}{sub 2} {yields} {zeta}{sub 2}{prime} transformation was previously studied by Subramanya et al. both for quenched and furnace-cooled specimens. They observed a considerable increase of the electric resistance for both the specimens, when they were aged slightly above the Ms temperature.