Study of the liquidus and solidus surfaces in the quaternary Fe-Ni-Cu-S system: IV. Construction of a meltability diagram and determination of miscibility gap boundaries for the ternary Cu-Fe-S sulfide system

The phase transformations in the ternary sulfide Cu-Fe-S system are analyzed, and the positions and temperatures of the nonvariant equilibrium points and the monovariant equilibrium lines in this system are determined. Experimental results obtained by differential thermal analysis, scanning electron microscopy, and electron-probe microanalysis are used to plot projections of the liquidus and solidus surfaces on a concentration triangle, and the positions of the miscibility gap boundaries in the Cu-Fe-S system are determined. The composition and temperature of the critical miscibility gap point are determined, and conode directions are indicated. This work is the final part of a series of works dealing with the phase transformations occurring in the ternary systems that bound the quaternary Fe-Ni-Cu-S system.