Effect of Heterogeneous Microstructure on Refining Austenite Grain Size in Low Alloy Heavy-Gage Plate

作者：Shengfu Yuan, Z.J. Xie, Jingliang Wang, Longhao Zhu, Ling Yan, Chengjia Shang, R.D.K. Misra · 发表于：Metals · 年份：2020 · DOI：10.3390/met10010132 · 被引用次数：8 · 研究领域：Microstructure and Mechanical Properties of Steels、Metal Alloys Wear and Properties、Metallurgy and Material Forming

The present work introduces the role of heterogeneous microstructure in enhancing the nucleation density of reversed austenite. It was found that the novel pre-annealing produced a heterogeneous microstructure consisting of alloying elements-enriched martensite and alloying-depleted intercritical ferrite. The shape of the martensite at the prior austenite grain boundary was equiaxed and acicular at inter-laths. The equiaxed reversed austenite had a K-S orientation with adjacent prior austenite grain, and effectively refined the prior austenite grain that it grew into. The alloying elements-enriched martensite provided additional nucleation sites to form equiaxed reversed austenite at both prior austenite grain boundaries and intragranular inter-lath boundaries during re-austenitization. It was revealed that prior austenite grain size was refined to ~12 μm by pre-annealing and quenching, while it was ~30 μm by conventional quenching. This is a practical way of refining transformation products by refining prior austenite grain size to improve the strength, ductility and low temperature toughness of heavy-gage plate steel.