Experimental determination and thermodynamic modeling of phase equilibria in the Cu-Cr system

Liquidus temperatures in the Cu-Cr system at compositions of 10.0-72.7 at.% Cr were determined using electromagnetic levitation melting. The present data agree with the prediction of a recent thermodynamic study of the system for compositions up to 20.0 at.% Cr. However, they show large and positive deviations for other compositions. Microscopic studies reveal that compositions between 10.0 and 50.5 at.% Cr solidified into a dendritic microstructure, whereas those between 55.9 and 72.7 at.% Cr solidified into a droplet-shaped microstructure. The microstructure of the latter type provides direct evidence for the existence of a stable miscibility gap over Cr-rich compositions. Phase equilibria in the Cu-Cr system were calculated using the CALPHAD method. A novel phase diagram was proposed for the Cu-Cr system, which shows a monotectic reaction between compositions of 50.8 and 83.2 at.% Cr at an invariant temperature of 2020 ± 22 K. The novel phase diagram has reduced the discrepancies between the literature data.