Abstract
The authors proposed a modified heat treatment process for a medium Mn steel (Fe-5%Mn-0.1%C), namely, interrupted quenching and intercritical annealing (IQ-IA) 1), which enabled the stability of retained austenite to increase by high-temperature annealing without losing high-strength. In this process, IA was performed at approximately 900 K under the coexistence of martensite and untransformed austenite after the first IQ between the Ms and Mf temperatures. During IA, the reversed austenite grew in both width and length. As the annealing temperature was not high enough for the long-range diffusion of Mn, Mn enrichment occurred only in the space swept by the moving austenite/martensite interface. Thus, the Mn in the original part remained average in concentration. After cooling to ambient temperature, the Mn-enriched region remained as austenite, while the Mnnon- enriched original austenite region transformed to martensite (fresh martensite).
NSTL