Deformation twinning feature and its effects on significant enhancement of tensile ductility in columnar-grained Fe–6.5wt.%Si alloy at intermediate temperatures

The tensile deformation behavior of columnar-grained Fe–6.5wt.%Si alloy with <100> fiber texture at intermediate temperatures (300–500 °C) was investigated. Compared with equiaxed-grained Fe–6.5wt.%Si alloy, the enhanced tensile ductility and its mechanism of columnar-grained Fe–6.5wt.%Si alloy were mainly studied by the analysis of tensile twinning Schmid factor value and the deformation microstructure. The results showed that tensile ductility of the Fe–6.5wt.%Si alloy with columnar grains were increased significantly, i.e., the elongation of the columnar-grained specimens were increased to 6.6% (300 °C), 51.1% (400 °C), 51.3% (500 °C), which, respectively, corresponded to an increase of 3.7%, 25.8% and 23.2% compared with that of the equiaxed-grained specimens. The analysis of tensile twinning Schmid factor value and the deformation microstructure both demonstrated that deformation twinning occurred locally in the equiaxed-grained Fe–6.5wt.%Si alloy, while a great number of twins formed homogeneously in the columnar-grained Fe–6.5wt.%Si alloy. The significant enhancement of tensile ductility of the columnar-grained Fe–6.5wt.%Si alloy at intermediate temperatures was mainly ascribed to the formation of a great number of homogeneous deformation twins.