Observation of annealing twin nucleation at triple lines in nickel during grain growth

Abstract : Three-dimensional near-field high-energy X-ray diffraction microscopy has been used to observe the formation of new twinned grains in high purity Ni during annealing at 800 °C. In the fully recrystallized microstructure annealed at 800 °C, twinned grains form along triple lines. Both the grain boundary character and the grain boundary dihedral angles were measured before and after the twin formed. These measurements make it possible to show that although each new twinned grain increases the total grain boundary area, it reduces the total grain boundary energy.