Crystallographic Orientation of the ε → α′ Martensitic (Athermal) Transformation in a FeMnAlSi Steel

Abstract

The presence of athermal e- and α-martensite (α′) in the as-cast structure of a Fe-0.08C-1.95Si-15.1Mn-1.4Al-0.017N alloy has been revealed by electron backscattered diffraction analysis. The alloy exhibited two athermal martensitic transformations described by γ → α′ and γ → e → α′. The Shoji–Nishiyama orientation relationship was observed between γ-austenite and e-martensite, while α-martensite nucleated from γ-austenite exhibited a Kurdjumov–Sachs orientation relationship. Six crystallographic variants of α-martensite consisting of three twin-related variant pairs were observed in e-bands. A planar parallelism of {0001}e || {110}α′ and a directional relation of \( \left\langle {1\bar{1} 1} \right\rangle \alpha ' \) lying within 1 deg of \( \left\langle {\bar{1} 2\bar{1} 0} \right\rangle \varepsilon \) existed for these variants.