Dependency of deformation twinning on grain orientation in an FCC and a HCP metal

Twinning plays important roles in HCP metals and those FCC metals with low stacking fault energy. The structural difference of two types of metals makes quite different contributions of twinning to plasticity. The variety of grain orientation in polycrystalline metals causes the inhomogeneous occurrence of twinning and further distinct transformation kinetics of twinning as strain increases and texture develops. This changes finally the work hardening behavior and mechanical properties. This paper reveals the dependency of twinning on grain orientation in an FCC TWIP (twinning induced plasticity) steel with high Mn content and in a magnesium alloy using electron-backscatter-diffraction (EBSD) technique, and analyzes the characteristics of twinning in the two types of metals by Schmid factor calculation. In addition, the relation of twinning and shear banding, as well as their influence on properties are discussed.