Strength-ductility synergy in a 1.4 GPa austenitic steel with a heterogeneous lamellar microstructure

1.Introduction Advanced high-strength steels with good ductility are essen-tial to the manufacturing,structural safety,and light-weighting of load-bearing structures in many industries[1-3].Austenitic stain-less steel(ASS)exhibits high ductility due to the TRIP and/or TWIP effect that can alleviate stress concentration,prevent void nucle-ation,enhance work hardening,and postpone necking[4-6].The yield strength of conventional ASS is generally low(∼200-500 MPa),and their deformation resistance is insufficient for many load-bearing applications[6].Previous studies reported the in-creased yield strength in various austenitic steels through grain refinement,dislocation strengthening,precipitation strengthening,and heterogeneous hardening[7-14].A single strengthening mech-anism,however,is typically insufficient to obtain ultrahigh yield strength over 1 GPa in austenitic steel[12].