Experimental determination and thermodynamic modeling of phase equilibria in the Cu–Cr system
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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.
KeywordsLiquidus Temperature CALPHAD Method Electromagnetic Levitation Monotectic Temperature Measured Liquidus Temperature
This study is financially supported by the National Natural Science Foundation of China (50571025 and 50871078) and by the Ministry of Education (NCET05-0292). The authors thank Dr. H. Nagaumi for providing high purity chromium material. The authors also thank Dr. Jingbo Li for discussions. The authors are indebted to Mr. G. Luo for his assistance in experimental work.
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