Orthorhombic martensite formed in L12-type Fe3Pt Invar alloy

The tetragonality c / a of FCT martensite phase in an Fe 3 Pt depends on the degree of order S of the L1 2 -type parent phase. As the degree of order increases, the tetragonality c / a changes from being less than 1 ( S = 0.75) to being larger than 1 ( S = 0.88). In this study, we have investigated a martensitic transformation behavior in a single-crystalline Fe 3 Pt with a degree of order which is in between 0.75 and 0.88, and have found the existence of orthorohombic martensite phase in the Fe 3 Pt.