Shape Memory Effect and Anelasticity Associated with the Martensitic Transformation in the Stoechiometric Fe₃Pt Alloy

Abstract

We have studied the behavior of the iron-platinum alloys of the Fe₃Pt type subjected to various mechanical conditions before, during and after the martensitic transformation. Previous papers (1) (2) and (3) have shown that the characteristics of this martensitic transformation depend strongly on the long range order state of the parent austenitic phase; the M_s temperature is lowered as the degree of order is raised. When the order parameter S is ≥ 0,60, the transformation is thermoelastic (2) (3), and when this parameter is < 0,60, the transformation exhibits an appreciable thermal hysterisis. We have shown that the value S = 0,60 defines a limiting order parameter from which the disordering of the stoechiometric Fe₃Pt alloy becomes a two-phase process. We shall report in this paper the results obtained in our study of the Shape Memory Effect (S.M.E.), superelasticity (or pseudo-elasticity), transformation plasticity and the internal friction. Theses effects are all related to the martensitic transformation and they will be discussed in connection with the initial order state of the austenite.