Quantitative prediction of grain boundary misorientation effect on twin transmission in hexagonal metals

Intergranular twinning shear transmission through twin-twin accommodation, which plays an important role on microstructure evolution, is often observed in deformed hexagonal metals. The shear transmitted between two connected twins is m's, where m' is the geometrical compatibility factor and s is the magnitude of the original shear. However, the quantitative correlation between the grain boundary misorientation (GBM) and m' factor for shear transmission is unknown. In the present study, we developed an m'-GBM map to tackle this problem. The map is applied to {11 (2) over bar2}-{11 (2) over bar2}, {11 (2) over bar2}-{11 (2) over bar4} and {11 (2) over bar4}-{11 (2) over bar4} twin pairs in Ti, which have rarely been reported before but are profuse in a cryorolled state. Favorable GBM for the formation of these twin pairs is revealed by the map. Specifically, the map shows that low GBM angles (<15 degrees) are conducive to the formation of {11<(2)over bar>2}-{11 (2) over bar2} and {11 (2) over bar4}-{11 (2) over bar4} twin pairs. The map also reveals that both the {11 (2) over bar2}-{11 (2) over bar2} and {11 (2) over bar2}-{11 (2) over bar4} twin pairs tend to occur at grain boundaries with media angles (15 degrees-45 degrees), depending on the location of the corresponding GBM axis in the m'-GBM map. These predictions were then verified by experimental analysis. (C) 2020 The Authors. Published by Elsevier Ltd.