Effect of roll speed ratio on microstructure evolution and mechanical properties of 0.18 wt% carbon steel deformed by differential speed rolling

• Effect of roll speed ratio on microstructure and properties of steel samples was significant.
• High fraction of ultrafine grains was achieved after 4-pass DSR at the roll speed ratio of 1:4.
• Ultimate tensile strengths of steel samples were improved with increasing roll speed ratio.

This work investigated the microstructural development and mechanical properties of 0.18 wt% carbon steel samples fabricated using a differential speed rolling (DSR) technique with respect to the roll speed ratio. For this purpose, the samples were deformed by up to 4-pass DSR at room temperature using three different roll speed ratios, including 1:1, 1:2 and 1:4 for the lower and upper rolls, respectively. The microstructural observations showed that, after 4-pass DSR at a roll speed ratio of 1:4, most of the ferrite grains were refined significantly to ~0.4 µm in diameter. Tensile test results showed that, as the roll speed ratio increased, the strength increased significantly while sacrificing tensile ductility.