Influences of Processing and Composition on the Grain Boundary Character Distribution

Experiments were performed to observe the effects of processing and composition on the grain boundary character distribution (GBCD) of SrTiO3, MgO, and Ni. Anisotropic interfacial energies and, in the case of nickel, crystallographic constraints, are expected to influence the evolution of the GBCD during processing. Interrupted grain growth experiments were performed with SrTiO3 to observe the evolution of the GBCD with grain growth. The GBCD was determined at three time steps during grain growth and quantitative comparisons were made. Guidelines for quantitative comparisons of grain boundary plane distributions (GBPDs) and GBCDs were established Relative grain boundary energies were evaluated using two independent techniques to observe the relationship between grain boundary populat ion and energy and the role that grain boundary energy has in determining the GBCD. It was found that anisotropic interfacial energies dictate an anisotropic GBCD which develops very early in the grain growth process for SrTiO 3. The GBPD remains constant even as the grain size increases. Relatively low energy {100} grain boundary planes are favored. The five parameter GBCD evolves during grain growth to eliminate relatively higher energy grain boundaries while lower energy grain boundaries are preserved. Doping was explored as a processing technique to alter the GBCD in MgO. The GBCDs of 3000 ppm Ca-doped MgO and undoped MgO were measured and quantitatively compared. Relative grain boundary energy anisotropy was determined for each material and compared to the anisotropy of the GBPD.