Microstructural evolution and formation mechanism of bimodal structure of 0.2% carbon steel subjected to the heavy-reduction controlled rolling process

A heavy-reduction controlled rolling process with approximately 75% thickness reduction was carried out to investigate the microstructural evolution including texture development, focusing on the formation of a bimodal structure of 0.2% carbon steel with heating temperatures of 700, 800, 900, and 1000 °C. Upon increasing the heating temperature from 700 to 900 °C, the microstructure was refined and precipitates such as Fe3C were uniformly distributed throughout the microstructure. For the microstructures control-rolled at heating temperatures of 900 and 1000 °C with average ferrite grain sizes of 1.34 and 1.63 μm, respectively, a bimodal structure could be observed by scanning electron microscopy (SEM), which was very similar to the result of a plane-strain compression (PSC) test. Moreover, the 900 and 1000 °C-heated specimens had less well developed textures primarily consisting of {113}-{4 4 11}〈110〉 and {332}〈113〉 components, which usually developed by the transformation (γ→α), and the 1000 °C-heated specimen exhibited various textures and a low intensity of the {100}〈011〉 component, which was generally transformed from the {100}〈001〉 component of the recrystallized austenite.