Experimental investigation of the Mo–Ni–Re system

Abstract

Isothermal sections of the Mo–Ni–Re system have been investigated at 1200°C and 1600°C by characterization of the equilibrated arc melted alloys with the help of electron probe microanalysis (EPMA) and X-ray diffraction (XRD) techniques. The 1200°C isothermal section proposed during the present study showed large extension of the Mo–Re σ phase and Mo–Ni δ phase in the ternary region. In addition, presence of two previously unknown ternary phases (a phase with structure prototype Mo3CoSi and another having a modulated σ structure) was also observed. The isothermal section of the Mo–Ni–Re system at 1600°C also showed large extension of σ phase in the ternary region whereas extension of Mo–Re χ phase in both isothermal sections was restricted to only few at.% Ni. The presence of the ternary phases observed in the 1200°C isothermal was not evidenced in 1600°C isothermal sections. In addition to the phase equilibria investigation in the ternary system, partial determination of the phase equilibria in the Mo–Ni and Mo–Re systems, and of the liquidus projection of the Mo–Ni–Re system was also carried out. The liquidus projection of the Mo–Ni–Re system proposed during present study showed extended primary crystallization fields of the σ and (Re) phases.