Revealing extraordinary plasticity in single crystal Fe-15Mn-10Cr-8Ni-4Si alloy

Abstract

An extraordinary elongation of over 156 % was achieved in single crystal Fe-15Mn-10Cr-8Ni-4Si alloy, which shows γ → ε → α’ transformation. Tensile tests were conducted along the 〈414〉, 〈111〉, and 〈100〉 directions, and the deformed microstructure was characterized with electron-backscattering diffraction (EBSD). Elongation in 〈414〉 orientation (156 %) was highest as ever recorded in metallic alloy—approximately twice that of conventional TWIP steels. Mechanical behavior in 〈414〉 is characterized with slow work hardening, with upward curvature in the stress–strain curve. EBSD analysis revealed 45 % of ε-martensite and significant γ-twin microstructure components in 〈414〉. In initial stage, deformation was marked by planar slip and a sluggish γ → ε transformation, activating a single ε-martensite variant with a Schmid factor of 0.5. Later stages witnessed crystal rotation towards 〈112〉, generating multiple shear bands and distinct ε variants. Fractures predominantly occurred along the 〈011〉 direction, with the fracture surface exhibiting a ductile nature.