Hot Deformation Behavior of Fe-2%Si

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The hot deformation behavior of a high purity binary ferritic Fe-2 mass% Si alloy, undergoing no phase transformation or precipitation reactions, was investigated by hot torsion tests. The parameters for the constitutive equation of Fe-2 mass% Si steel were experimentally determined from the stress-strain curves. The activation energy for hot deformation was close to that for lattice self-diffusion in α-Fe, indicating that hot deformation of Fe-2 mass% Si steel occurs by a thermally-activated, diffusion-controlled dislocation climb mechanism. The electron backscattering diffraction technique and transmission electron microscopy were used to analyze the microstructural changes occurring during hot deformation. It was found that the hot deformed microstructure consisted of equiaxed crystallites surrounded by a high proportion of high angle boundaries. These boundaries were homogeneously distributed in the microstructure. A gradual increase in the fraction of boundaries with a misorientation in the range of 10° to 18° was observed in samples obtained from interrupted torsion tests. The formation of high angle boundaries at temperatures above 0.5Tm is attributed to a gradual increase of the misorientation of low angle boundaries by the absorption of dislocations.