Grain Size and Texture Evolution During Annealing of Non-oriented Electrical Steel Deformed in Tension

Abstract

The evolution of grain size and texture during annealing at 700 °C of a low C, Si-Al electrical steel strip is investigated in samples deformed between 3 and 25% in tension. After an incubation period, which decreases as the magnitude of the pre-deformation increases, the grain size-time relationship exhibits two different stages. Initially, the grain growth occurs in some especial grains until they consume the deformed microstructure. In contrast, during the second stage the rate of growth decreases rapidly and a final constant grain size is reached which depends strongly on the initial deformation. Analysis of EBSD data obtained from strained samples shows that there is a direct relationship between the magnitude of the prior tensile strain, the intergranular misorientations as estimated by the grain orientation spread (GOS) and the image quality parameters. An attempt to explain the recrystallization texture observed in terms of the Taylor factors for some orientations in the α fiber of the deformation textures was made, nevertheless this analysis was not entirely satisfactory. However, it was found that the main orientation components present in the recrystallization texture of annealed samples are those with lower internal misorientation (lower GOS) in the deformed material. These results suggest that, in the material investigated, recrystallization after tensile deformation takes place via strain-induced boundary migration during annealing. Estimation of energy losses due to magnetic hysteresis in annealed samples show that the energy losses decrease as the grain size increases and as the texture factor defined as the ratio between the volume fractions of detrimental and beneficial orientations for magnetic properties, $f\{ 111\} + f(112)[1\overline{1}0] + f(110)[1\overline{1}0])/f\{ 001\}$, increases.