Determination of the non-chemical free energy terms in martensitic transformations

In former papers we proposed a method for the determination of the volume derivatives of dissipative and elastic free energy contributions at the start and finish temperatures of the martensitic transformation. This analysis can be extended and from the normalized hysteresis loops the non-chemical free energies can be calculated at different transformed fractions. The self-consistency of the extended analysis is illustrated on the basis of hysteresis and differential scanning calorimetry measurements in polycrystalline Cu–Al–Ni shape memory alloys. In single-crystalline samples of the same alloy, the equilibrium transformation temperature has also been determined as the function of the uniaxial stress, which can make the above analysis complete and allows the determination of the absolute values of the elastic energy contributions as well.