Structure and Phase Composition of Ni–Al–Cr Alloy Alloyed by Rhenium and Lanthanum

Abstract

The paper presents the transmission and the scanning electron microscope investigations of the phase composition and fine structure of Ni–Al–Cr-based alloy alloyed by rhenium and lanthanum. The alloy is prepared by the directional crystallization technique and then subjected to 1150°С annealing during 1 hour. It is shown that γ- and γ′-phases are major and have a face-centered cubic crystal system. Solid solutions of γ- and γ′-phase have a disordered and an ordered atom arrangement, respectively. The latter has L12 superstructure. It is found that rhenium and lanthanum alloying leads to the structural modification of γ′-phase quasi-cuboids. Not dissolving in major phases, rhenium and lanthanum are phase-formation elements and form σ-phase. The phase composition and morphology of these phases are studied and described.