Austenite Nucleation and Growth as a Function of Starting Microstructure for a Fe‐0.15C‐5.56Mn‐1.1Si‐1.89Al Medium‐Mn Steel

The effects of starting microstructure and intercritical annealing temperature on the phase-transformation kinetics microstructural evolution a prototype Fe–0.15C–5.56Mn–1.1Si–1.89Al medium-Mn third-generation advanced high-strength steel are examined. microstructures comprise 1) an as-received cold-rolled (CR) containing significant fraction ferrite tempered martensite 2) austenitized quenched martensite–ferrite (MF) microstructure. Based observations, two different scenarios for austenite formation during proposed. For CR microstructure, can nucleate at ferrite/cementite interfaces, grain boundaries. In case MF which contains thin films interlath retained (RA), forms lath boundaries or grows directly from existing RA. studies interpreted using DICTRA module Thermo-Calc. At 665 °C, reversion samples faster than transformation in structure. higher temperatures where most cementite has dissolved, both is very similar.