Deformation twinning in an Fe-6.5 wt.% Si alloy with columnar grains during intermediate temperature compression

Deformation twinning in coarse-grained body-centered-cubic (BCC) metals with medium to high stacking fault energy only took place during plastic deformation at low temperature or high strain rate conditions. However, in this study deformation twinning was found in an Fe-6.5 wt.% Si alloy (BCC) after intermediate temperature compression by electron backscattered diffraction and transmission electron microscope. Deformation twin with the twinning system of {1 1 2} 〈1 1 1〉 appeared in the Fe-6.5 wt.% Si alloy after compression at 400 °C, strain rate of (2–3) × 10−3 s−1 and compression amount more than 5.8%. Dislocation density inside the deformation twin was much higher than that inside the matrix and the dislocation could slip through most of twin boundary easily. It is indicated that plastic deformation of the Fe-6.5 wt.%Si alloy with columnar grains can be favorably achieved by twinning mechanism at intermediate temperature when the dislocation slip is difficult to activate. On the other hand, deformation twinning can adjust the crystallographic orientation of the grains, which is beneficial to the activation of dislocation slip.

► Twinning was found firstly in Fe-6.5 wt.% Si alloy during compression at 400 °C. ► Twinning makes the grains get better orientation for activating dislocation slip. ► Dislocation density inside the twin is much higher than that inside the matrix. ► Dislocation could slip through most of twin boundary easily.