Effect of hydrostatic pressures on thermoelastic martensitic transformations

Abstract

Supposing that - according to the Clausius-Clapeyron equation - the volume change of the transformation is responsible for the pressure dependence of the equilibrium temperature T o , and that the elastic energy term, e o , corresponding to the martensite start, M s , (and austenite finish, A f, ) temperatures, differs from zero as well, the pressure dependence of the elastic and dissipative energy terms of the martensitic and reverse transformations can be separated. It is illustrated by the example of our experimental results for the pressure effect on the transformations in Cu-22at%Zn-12at%Al-1at%Mn [1] as well as in near equiatomic NiTi shape memory alloys [2]. The elastic energy term, e o , showed different behaviour in the low-pressure range for samples of different pre-history, while at high pressures the pressure dependence of the elastic and dissipative terms showed a more general trend.