Stacking Fault Energy-Dependent Strategy Induces Fourfold Nanotwins to Circumvent Strength-Ductility Tradeoff In Medium Manganese Steel

Abstract

Two successive cycles of deformation were conducted in corresponding stacking fault energy (SFE) ranges dominated by dislocation slip and twinning deformation. This SFE-dependent deformation process yields a sample with high-density dislocations, stacking faults (SFs) and four-fold nanotwins. Dislocation hardening and SFs-assisted acceleration of martensite transformation result in excellent work hardening capacity and consequently high strength. Meanwhile, nanotwins provide superior ductility by alleviating shear strain accumulation and retarding crack initiation. The SFE strategy increased the yield strength of the present sample by 3.1 times without sacrificing ductility, thereby overcoming the strength–ductility tradeoff.