The formation mechanism of reverted austenite in Mn-based maraging steels

Based on the microstructural evolution in Mn-based maraging steels aged at 460–540 °C, the formation mechanism of reverted austenite is proposed. Reverted austenite formed at grain boundaries at the onset of aging. During further aging, the accumulated Mn enrichment at newly formed α′/γ interfaces led to thin austenite layers growing into lath-like austenite grains. The lateral growth of lath-like reverted austenite was sluggish, reflecting the low diffusivity of Mn. We show that reverted austenite formed by a shear-dominated mechanism assisted by a small amount of Mn diffusion, whereas the nucleation of reverted austenite within martensite laths was kinetically slower.