Experimental Investigation in the Quaternary Systems Ti–Ni–Al–N and Ti–Ni–Al–O (original) (raw)

The experimental evaluation of phase equilibria in the Ti+Ni+Al+N and Ti+Ni+Al+O phase diagrams are based on alloy samples, which were prepared of elemental powder blends by argon-levitation melting in a Hukin crucible. The experimental investigation employed X-ray powder di4raction, metallography, SEM, and EMPA techniques in the as-cast state as well as after annealing at 9003C. Two quaternary compounds Ti 3 NiAl 2 N and Ti 3 NiAl 2 O deriving from the 5lled Ti 2 Ni type (phase) were observed. The novel phases are in equilibrium with the Ti 2 Ni-type solid solution phase (Ti 1؊x Al x) 2 Ni, which exhibits a maximum solubility of 14 at.% Al in binary Ti 2 Ni. Atom order in all these phases was monitored by quantitative X-ray powder di4raction (Rietveld analyses). The di4erence of X-ray spectra among the various phases deriving from parent Ti 2 Ni type was analyzed and the complex atom site occupation mode was discussed in terms of the general classi5cation scheme for phases.