ISOTHERMAL BCC-DOUBLE-LEFT-RIGHT-ARROW-FCC PHASE-TRANSFORMATIONS IN FE-NI ALLOYS WITH A SUBMICROGRAIN STRUCTURE

A low-temperature (300-500 K) isothermal BCC double left right arrow F CC phase transformation was found to occur in Fe-Ni alloys having a su bmicrograin (SMG) structure produced by shear pressure (SP). The phase transformation is stimulated by irradiation with high-energy electron s (E similar to 5.5 MeV). The SMG structure of a binnly FeNi32 alloy, which is produced under a deformation pressure, undergoes either a alp ha-->gamma or gamma-->alpha isothermal phase transformation depending on the initial (before deformation) structure. gamma-phase or alpha-ph ase. Doping of the iron-nickel alloy with zirconium (FeNi35Zr4) promot es the gamma-->alpha isothermal transformation, while doping with tita nium (FeNi35Ti3) leads to stabilization of the alpha and gamma phase c omposition. If is inferred that the phase transformations are to be cl assified with martensitic phase transformations in a fine medium with large accumulated elastic distortions. (C) 1997 Acta Metallurgica Inc.