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Microstructural Analysis, Martensitic Transformation, Next-generation Cryogenic Fatigue Resistant Alloy

"Unveiling the transformation pathways of hierarchical γ90 – εtwin – α’ triple phase structure formation at ε-ε martensite intersection" ======== Deformation-induced martensitic transformation (γ-austenite → ε-martensite/α’-martensite) in austenitic steels has garnered significant interest owing to its transformation-induced plasticity effect. In our recent study, a hierarchical triple phase structure was discovered at ε–ε intersection, where the γ rotated 90º from the matrix (γ90), {10-12} ε-twin, and α’ phases coexist. Depending on the operative shear angle with a common intersection axis, either 90º (Type I) or 30º (Type II), three distinct atomic rearrangements of the intersection volume were observed: γ90 was present at Type I intersection, and α’-phase was developed at Type II intersection, respectively. {10-12} ε-twin also occurred at Type I intersection, serving as an accommodation mechanism alongside the intersection γ90. Transformation paths for three intersection products were visualized by the unified tetrahedron model, considering T/2 or T/3 γ-twinning shear as an intermediate state. Moreover, a novel scheme is proposed to index the α’-martensite crystallographic variants at ε-ε intersections by establishing a correlation between the Bain distortion and double shear process.


Society memberships

The Minerals, Metals & Materials Society (TMS)


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