Formation of {100} Subgrain Variants and Σ3 Variants During Phase Transformation of Columnar Grains in Electrical Steel: Texture Memory and Variant Selection

Abstract

The columnar grains are composed of near‐{100} subgrain variants, Σ3 variants, and untransformed coarse columnar grains. As the Si content increases from 0.35% to 1%, the untransformed columnar grains are remarkably reduced, but the {100} subgrain variants still exist significantly. The phase transformation strain induced by {100} subgrain variants is large, while that induced by small equiaxed grains, which conform to Σ3 relationship with columnar grains, is lower. During the twice‐phase transformations, even if the variants appear randomly, the probability of occurrence of the {100} variants is 33.3%. Moreover, the {100} subgrain variants mainly appear as single variants because the phase transformation strain of the single variant, which is independent of orientation, is higher than that of the variant pair. Although the strain energy of the {100} subgrains has no advantage, the low‐angle grain boundary interface energy is lower than other high‐angle grain boundaries except for Σ3, which contributes to the appearance of the {100} subgrain variants. The appearance of the Σ3 relationships is to reduce the overall energy, rather than the simple strain accommodation behavior between variants. Beyond that, the actual phase transformation does not follow the strict K−S relationship.