Electron backscatter diffraction and performance of a severely deformed steel

This study investigated electron backscatter diffraction and performance of ultrafine-grained interstitial-free (IF) steel fabricated by an asymmetric rolling process (ASR). For ASR operations, plastic strain was induced with a thickness reduction of 30% per pass and a roll speed ratio of 1:4 for the lower and upper rolls, respectively. As the number of operations increased, the deformed microstructure developed gradually from a band-like structure, which was observed after a single pass, to almost equiaxed ultrafine grains (~0.7 μm) divided by high-angle boundaries after 4-pass ASR. The mechanical behaviors analyzed by microhardness and tension tests showed that the mechanical strength of the IF steel samples improved with increasing number of ASR operations, which was associated with the structural refinement and textural evolution in the ASR-deformed sample.