Surface severe plastic deformation-enabled deformation behavior control and mechanical property enhancement in metastable ferrous medium-entropy alloys

Gu, G. H.*; Jeong, S. G.*; Lee, J. H.*; Harjo, S.   ; Gong, W.   ; Amanov, A.*; Bae, J. W.*; Kwon, H.*; Kim, H. S.*

Gu, G. H.*; Jeong, S. G.*; Lee, J. H.*; Harjo, S.; Gong, W.; Amanov, A.*; Bae, J. W.*; Kwon, H.*; Kim, H. S.*

Stacking fault energy (SFE) controls key deformation mechanisms in metals. This study demonstrates that apparent SFE and deformation behavior can be tuned by modifying only the near-surface microstructure (100 um) through surface severe plastic deformation. The resulting gradient microstructure reduces apparent SFE, promoting martensitic transformation via preferential nucleation and stress partitioning. Consequently, mechanical properties are enhanced, achieving higher strength with minimal ductility loss, highlighting the effectiveness of localized microstructural engineering.