Effect of hydrostatic pressure on the cubic-orthorhombic phase transformation in Au-47·5 at % Cd alloy

Abstract

The effect of hydrostatic pressure, up to 10 kbar, on the martensitic cubic-orthorhombic (β·β′) transformation in Au-47·5 at.% Cd alloy was investigated by measurement of the variation of electrical resistivity. It was found that the β·β′ phase change in this alloy can be induced by hydrostatic pressures under isothermal conditions. The effect of hydrostatic pressure on the transformation temperature is identical with the effect of temperature on the transformation pressure. It was found to be 2°K kbar⁻¹. This temperature-pressure effect is consistent with the observed hystereses in Au47·5 at.% Cd alloy. From the experimental results, the heat of transformation and the transformation entropy have been calculated, and found to be 184 cal mole⁻¹ and 0·54 cal mol⁻¹ deg⁻¹, respectively. It was also observed that the temperature hysteresis width, and the driving force of this martensitic transformation, are not affected by hydrostatic pressure. The driving force for this phase change was calculated to be 2·8 cal/mol, which is remarkably small for a martensitic transformation.