Nucleation and growth of twins in Zr: A statistical study

An in-depth statistical analysis using electron backscatter diffraction (EBSD) is carried out to expose statistical correlations between {101¯2} twinning and grain size, crystallographic orientation, grain boundary length, and neighbor misorientation in high-purity polycrystalline zirconium strained to 5% and 10% at 77 K. A strong correlation was found between the active twin variant and crystallographic orientation. The propensity of a grain to twin or not was found to be only weakly dependent on grain area and diameter. Within the population of grains containing twins the number of twins per grain noticeably increases with grain area, and twin thickness is found to be rather insensitive to grain size and orientation. A weak preference for twinning was found for smaller grain boundary misorientation angles. These and the other statistical results reported can improve theoretical treatments for twin nucleation in polycrystal models. The statistical methodology presented has general applicability for all twin types in a wide range of metals.