The relative energies of 43 large-angle grain boundaries in Ni-rich NiAl were determined with the aid of scanning probe microscopy, using the thermal grooving method at 1400C. The geometrical degrees of freedom of the same grain boundaries were also characterized by using a combination of electron back-scattering diffraction and serial-sectioning techniques. It was found that the ratios of the grain-boundary to the surface energy were scattered over the range: 0.2 to 1.1. Twist grain boundaries exhibited higher energies than did the tilt counterparts. Mixed grain boundaries with approximately equal degrees of tilt and twist component did not exhibit high energies. A marked dependence of the energy of a large-angle grain boundary with fixed misorientational degrees of freedom on its plane inclination was demonstrated. The energies of selected grain boundaries and free surfaces in NiAl were calculated by using an embedded-atom method interatomic potential which was especially developed for NiAl. The calculated energies of Ʃ5 (210)[001], Ʃ5 (210)[001], Ʃ5 (310)[001], Ʃ5 (310)[001], Ʃ3 (211)[011] and Ʃ3 (111)[011] boundaries were 980, 886, 1066, 1148, 459 and 734mJ/m2, respectively. 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