The metastable liquid miscibility gap in Cu-Co-Fe alloys

The metastable liquid-phase separation (MLPS) in the Cu-Co-Fe system was investigated using an electromagnetic levitation melting and solidification technique. It was found that when ternary alloys containing more than 10 wt.% (12 at.%) Co and 10 wt.% (11 at.%) Fe were undercooled below a certain temperature, T-sep, the homogeneous melt separated into two liquid phases. In alloys containing more than 54 to 57 wt.% (49 to 54at,%) Cu (depending on the Co and Fe content), the phase separation generally appeared as dispersed (Fe, Co)-rich droplets (L-1) in a Cu-rich matrix, whereas for alloys containing less copper, the separation resulted in Cu-rich droplets (L-2) in a (Pe, Co)-rich matrix. The metastable liquid miscibility gap boundary of the Cu-Co-Fe ternary was determined using the measured T-sep and the composition of the separated phases. The ternary liquid-phase separated boundaries were found to be consistent with a cross-sectioned phase diagram in which one axis represents pure copper and the other Fe + Co.