Microstructures and mechanical properties of commercial purity iron processed by asymmetric rolling

For the purpose of grain refinement, commercial purity iron processed by asymmetric rolling (ASR) has been studied by optical microscopy, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Equiaxed ultra fined grains with a grain size of about 0.9 μm and a large fraction of high angle grain boundaries were obtained. The formation of the equiaxed grains is suggested to result from the additional shear strain which is observed by the shape change of a Cu band inserted into the rolled materials. The rolled iron exhibits high yield strength with a low work hardening ability and high microhardness, which are attributed to the high dislocation density and the large fraction of the high angle boundaries.