New observations on the formation of athermal martensite in Fe–Ni–Mo alloys

The thermally induced γ–ɛ and γ–α′ martensitic transformation in Fe–30%Ni–x%Mo alloys with different Mo contents have been studied by transmission electron microscopy (TEM). Observations reveal that α′ martensite is found in alloys containing 0.8, 1.8, and 2.6% Mo, and ɛ martensite in the alloy containing 5%Mo. The first three display the Kurdjumov–Sachs (K–S) orientation relationship between γ and α′, while the other displays the Shoji–Nishiyama (S–N) orientation relationship between γ and ɛ.