Precursor shear elastic pseudo-isotropy in near second order martensitic phase transitions

In contrast to the behavior of the isentropic elastic constants both isothermal constants, C' and C-44, of In-Cd, In-Tl and Fe-Pd alloys soften on approaching the martensite start temperature. The isothermal, i.e. low frequency, approximate to 500Hz, anisotropy ratio approaches a value of unity as the martensitic transformation is approached from above. The parent phase becomes shear elastically pseudo-isotropic. Close to the transition, this shear pseudo-isotropy reflects the reorientation of incipient variants in the cubic phase under the influence of the dynamic measuring stress. It represents a true dynamical precursor of this fee double left right arrow fct near second order martensitic phase transition.