Orientation Selective Martensite Transformation in an Fe-28Ni Alloy

Abstract

A variant selection phenomenon was studied during the phase transformation in an Fe-28%Ni alloy, which was slowly cooled to room temperature at a rate of 1°C/min after reheating to 1000°C, or warm rolled at 250°C during air cooling. The textures of parent and product phases were determined on the basis of local orientation measurements in the austenite and martensite phase. The measured product textures were compared with the modeled ones, which were obtained by applying the Bain, Kurdjumov-Sachs and Nishiyama-Wassermann transformation laws on the local austenite grains. It was shown that the presence of a deformation substructure is not an essential prerequisite for the occurrence of variant selection, The data reveal that a variant selection mechanism is active also in not deformed samples, containing a fully recrystallized parent matrix. The nature of the variant selection mechanism is discussed in terms of the elastic anisotropy of the parent phase.