Phase transformations in high chromium nickel alloys

A physico-chemical study is made of the ternary alloys Kh40NYu3 and Kh40NT4 and of quaternary alloys of the Kh40NYuT2 and Kh40NYuT3 types in which aluminium and titanium are alloyed together. It is established that, owing to decomposition of the γ-solid solution, a considerable amount of the α-phase is formed in Kh40NYu3 during annealing but decreases as the annealing temperature rises. In Kh40NYuT2, apart from decomposition of the γ-solid solution, formation of the α-phase is accompanied by an intermetallic γ-phase of the Ni3(Al, Ti) type with a face-centred cubic lattice, the lattice spacing being 3.59 A. The quantity of the α-phase in Kh40NYuT2 is lower than in Kh40Yu3, and increases as the annealing temperature rises from 700 to 8000C. Kh40NT4 was found to contain intermetallic phases of two kinds: α-Ni3Ti with a hexagonal lattice and β-Ni3Ti with a face-centred cubic structure. (author)