Investigation of phase equilibria related to fusion reactor materials: II. The ternary system Hf-Al-N

Phase equilibria in the ternary system Hf-Al-N are investigated. At 1273 K, the ternary phase Hf₃AlN (isotypic with Zr₃AlN, monoclinic, a = 0.59011 nm, 6 = 0.88646 nm, c = 0.33185 nm, β = 106.33°) coexists with HfN_1−x, A1N, Hf₂Al₃, HfAl, Hf₄Al₃, Hf₃Al₃ and -Hf(s.s.). At 1673 K, a second ternary phase Hf₅Al₃N (isotypic with Zr₅Al₃N_1−x, hexagonal, a = 0.8062 nm, c = 0.5603 nm) occurs. A1N in contact with hafnium or hafnium-rich Hf-Al alloys decomposes at this temperature into HfN_1−x and HfAl₂. No ternary solubilities are observed further to the extended solid solutions of -Hf.