A study of α′ martensite nucleation in the iron15% Mn alloy

Abstract

An electron microscopic investigation of the crystallography and morphology of the martensitic transformations in the Fe15% Mn binary system was conducted. The α′ bcc martensite was found to nucleate preferentially at the intersections of if ϵ hcp laths as thin platelets. The α′ thus generated is twinned about the {211} α′ and contains a substructure. A simultaneous electron microscopic evaluation of all three structures yielded the following orientation relations: {111} γ,〈110〉 γ∥{0001} ε,〈10 10〉 ε∥{110}α′,〈111〉α′ . The strained ϵ/α′ interface appeared to be described by the relationship: {113} γ,〈110〉 γ∥{10 11} ε,〈01 12〉 ε∥{211}α′,〈0 11〉α′ . An ϵ↔α′ transformation appears to occur. A crystallographic model is proposed to explain this ϵ↔α′ transformation and it is shown that the shape deformation in this model is substantially less than the Bain distortion for the γ↔α′ transformation.