Effect of intercritical heat treatment on the microstructure and mechanical properties of medium Mn steels

Abstract

In the present work, the effects of intercritical annealing parameters on the microstructure and cold rollability (deformation rate and ratio) of "3rd Generation Advanced High Strength Steels (AHSS)" were studied. Hence, this paper discusses the formation of microstructures with different volume fractions of ferrite, martensite, bainite and retained austenite (RA). Two novel microstructures have been created, based on two levels of manganese (Mn): (i) ferrite plus martensite nucleated in austenite microstructure (FMNA structures), using Mn levels of 5 to 7 wt% and (ii) ferrite plus retained austenite duplex structure (FADP steels) for a Mn level of 10 wt%. In general, the ductility is a function of the amount of retained austenite and the strength is highly dependent on the martensite level. © 2013 ISIJ.