Effect of grain boundary angle on {332}<113> twinning transfer behavior in β-type Ti-15Mo-5Zr alloy

The {332}< 113 > twin-twin and twin-dislocation pairs at various grain boundaries were systematically examined by using electron backscattered diffraction technique in a slightly deformed beta-type Ti-15Mo-5Zr alloy. The effect of grain boundary angle on twinning transfer behavior in neighboring grain was quantitatively analyzed in terms of strain accommodation combined macroscopic Schmid law. The twinning transfer occurred readily at the low angle grain boundaries without significant local stress concentration and formed a twin-twin pair dominated by applied stress, i.e., macroscopic Schmid law. At the high angle grain boundaries, it often resulted in a twin-twin pair with non-Schmid factor twinning variant or a twin-dislocation pair with geometrically necessary dislocations at the boundary area dominated by the strain accommodation. The activation of non-Schmid factor twinning variant and slip system in neighboring grain was due to their high accommodative capacity while releasing the local internal stress concentration, which was caused by the twinning transfer at high angle grain boundaries.