Alter martensitic phase transformation kinetics by forming Ni-rich nanolayer in metastable austenitic steels

Abstract

A 5 nm Ni-rich nanolayer has been introduced along nanoscale martensite/austenite phase boundaries (PBs) by one-step low-temperature annealing treatment of cold-rolled meta-stable austenitic steels. Control experiments reveal that the martensitic phase transformation kinetics can be significantly altered by presence of the nanolayers. The growth of pre-existed martensites is substantially suppressed while the martensite nucleation in austenites is less affected, as revealed by a statistical investigation on the martensite size distribution under different tensile strains. Enhanced strength and excellent ductility have been achieved simultaneously in the annealed samples, demonstrating that PBs can be effectively engineered to achieve optimized mechanical properties.