Crystallographic analysis of borides in Ni3Al base alloy IC6

A boride phase in a directionally solidified casting Ni3Al base alloy was investigated by means of scanning electron microscopy, transmission electron microscopy, X-ray mapping analysis, wavelength-dispersive X-ray analysis, electron energy loss analysis, energy-dispersive X-ray analysis and computer-aided dynamical diffraction simulation. This phase was observed to occur in the interdendritic region of the as-cast ingot. The chemical composition analysis and crystal structure studies revealed that the boride phase observed in the present alloy has a chemical formula of (Mo2Ni)B2, and a body-centered orthorhombic crystal structure with lattice parameters a = 0.703 nm, b = 0.474 nm and c = 0.312 nm. The space group of the phase was found to be Immm with the unit cell having 10 atoms which occupy the Wyckoff positions of Ni 2(a), Mo 2(b) and 2(c), and B 4(g).