Electron Microscope Study of the Martensite Transformation in an Ordered Fe₃Pt Alloy

Abstract

The martensitic transformation in an ordered Fe₃Pt alloy has been studied by means of electron microscopy. The bcc martensite was found to have a superlattice which was expected to be formed by the Bain distortion from the Cu₃Au type superlattice of γ phase. A number of transformation twins on the {112} type (not of the {211} and {121} types) plane were observed in the martensite. The habit plane of martensite plates and the orientation relationship between the martensite and austenite were consistent with those in the disordered Fe–Pt alloy of the same composition.
The domain structures in the ordered γ phase were observed by using the dark field method, and it was clarified that the Ms temperature dropped rapidly according as the size of domains increased.