Precipitation enhanced ultragrain refinement of Ti-Mo microalloyed ferritic steel during warm rolling

Ultragrain refinement caused by continuous dynamic recrystallization (cDRX) was studied from microstructure, texture and precipitation. Compared with microstructures of deformation induced ferrite transition (DIFT), ferrite matrix refined through cDRX presented more substructures. Textures formed through the cDRX mainly consisted of (001)[11¯0] and (111)[1¯1¯2] and the intensity of (001)[11¯0] could increase with strain. Rolling in γ non-recrystallization region facilitated the strain induced precipitation, hence more subboundaries formed during the subsequent warm rolling process. With the consumption of alloying elements, stability of remaining austenite was reduced and this promoted the formation of high temperature proeutectoid ferrite. Additionally, stress fields induced by the nanoscale precipitates could suppress the formation of microshear bands and further promote the generation of high angle boundaries, especially in the γ-fiber textures. Grains were refined to an average size of ~1 µm through cDRX and most refined grains transformed from γ-fiber textures presented an orientation of <110>//ND. Moreover, the refined matrix performed better mechanical properties along the rolling direction and the precipitation enhanced ultragrain refinement through cDRX showed greater potential on the refining of ferrite grains.