The relative energies of 43 different large angle grain boundaries in Ni-rich NiAl were determined with the aid of scanning probe microscopy using the thermal grooving method at 1400C. Simultaneously, the geometrical degrees of freedom of the same grain boundaries were characterized by a combination of electron back-scattering diffraction and serial sectioning techniques. The determined values of the ratio of the grain boundary to surface energy were scattered over a wide range of 0.2 to 1.1. It was found that twist grain boundaries exhibit higher energies than their tilt counterparts. Moreover, mixed grain boundaries with approximately equal amount of tilt and twist components did not exhibit high energies. A strong dependence of the energy of a large angle grain boundary with fixed misorientation degrees of freedom on its plane inclination was demonstrated. The energies of several selected grain boundaries and free surfaces in NiAl were calculated by employing an embedded-atom method interatomic potential specially developed for NiAl. The range of possible relative grain boundary energies estimated from these calculations was in a good agreement with experimental data.

Correlation between Grain Boundary Energy and Geometry in Ni-Rich NiAl. Y.Amouyal, E.Rabkin, Y.Mishin: Acta Materialia, 2005, 53[14], 3795-805

Table 6

Bulk Diffusivity of 67Ga in Ni3Al