Phase equilibria in the mischmetal-cobalt-iron system on the transition-metal-rich side

Abstract

A systematic study of phase equilibria in the commercially important mischmetal(MM)-Co-Fe system was made on the transition-metal-rich side. This investigation shows that most of the phases of the MM-Co system with high cobalt contents extend far into the ternary system; the phase of stoichiometry 2:17 possibly extends from RE-Co to binary RE-Fe where RE denotes the rare earth elements present in mischmetal. The RE₂(Co,Fe)₁₇ and RE(Co,Fe)₅ phases extend away from their respective stoichiometric lines towards the transition-metal-rich side. The RE₂(Co,Fe)₇ phase appears to be a new type of 2:7 phase. Three new ternary phases, designated as the S, T and A phases, were found to exist in the region of the ternary system investigated and the S phase was found to occur very close to and to run almost parallel to the 2:17 stoichiometric line. The diffraction patterns of all the new phases resemble the diffraction pattern of the 2:17 phase; the S phase structure is possibly a super lattice based on the 2:17 phase structure.