Precursor Shear Elastic Pseudo-Isotropy in Near Second Order Martensitic Phase Transitions

摘要

In contrast to the behavior of the isentropic elastic constants both isothermal constants, C and C^, of In-Cd, In-Tl and Fe-Pd alloys soften on approaching the martensite start temperature. The isothermal, i.e. low frequency, =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 *=> fct near second order martensitic phase transition.