Phenomenology of Elastic Properties in Martensite Alloys: II. Temperature Dependence of the Elastic Constant and Hysteresis Loop

Temperature dependence of the elastic stiffness constants in Martensite alloys with the symmetry change from the cubic m3m to the tetragonal 4/mmm and the orthorhombic mmm symmetries was discussed on the basis of the Landau-type free energy function expressed in terms of the strain components, u 1 , u 2 and u 3 . It was found that an elastic stiffness constant corresponding to the shear deformation, which behaves as a soft mode, becomes extremely small in the vicinity of the transition temperature. The strain–stress hysteresis loops near the transition temperature and the morphotropic phase boundary in the Martensite alloys were also discussed on the basis of the Landau-type free energy function. It was found that the coercive strain field in the stress–strain hysteresis loop decreases with approaching the morphotropic phase boundary, and vanishes there, because there the Landau-type free energy function becomes isotropic in the order parameter space.