Equilibria involving P- and (σ-phases in Ni–Cr–Al–Mo system

Abstract

An investigation is reported of phase equilibria in alloys of the Ni–Cr–AI–Mo system containing 60 and 50 at. –%Ni annealed at 1523 K. The experimental methods used mainly were electron microscopy, electron probe microanalysis, and X–ray diffraction. Four quaternary alloys were used, with compositions (at.–%) lying on a line between Ni₆₀Al₄₀ and Ni₆₀Cr₂₀Mo₂₀,and one alloy containing 50Ni–28Cr–10AI-12Mo.The composition range was chosen to include the P–and σ –phases based on the Ni–Cr–Mo system. The phases involved in equilibria at 1523 K in the 60 at. –%Ni alloy series were γ (Ni–base solid solution), β (based on NiAI), Mo–base solid solution, and P; the 50 at. –%Ni alloy contained γ, β and σ. Partial isothermal sections of the quaternary system at 60 and 50 at. –%Ni have been determined. Eutectics containing either γ + P or γ + β + P were present

in the as–solidified 60 at. –%Ni alloys, while a γ + β + σ eutectic was present in the 50 at–%Ni alloy; some compositional data for eutectic phases were obtained by analytical transmission electron microscopy. High hardness values (from ~ 500 to 670 HV) were obtained in the as–solidified alloys.

MST/265