Phenomenology of Elastic Properties in Martensite Alloys

The phase diagram and elastic stiffness constants in Martensite alloys with the symmetry change from the cubic m3m to the tetragonal 4/mmm and the orthorhombic mmm symmetries are 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 some of elastic stiffness constants corresponding to the shear deformation become extremely small not only in the vicinity of the transition temperature but also near the morphotropic phase boundary where the Landau-type free energy function is isotropic or less anisotropic in the order parameter space.