Phase Selection in Undercooled Melts of Peritectic Cu-Ge Alloys

Abstract:

Phase selection in undercooled melts of Cu-14.8Ge and Cu-18Ge compositions was investigated using the electromagnetic levitation technique in combination with substrate quenching and a drop tube. The results showed that the levitated and gas-cooled samples were all solidified into a microstructure consisting of primary -Cu plus peritectic -Cu5Ge. However, the samples quenched onto a copper substrate showed a segregation-free microstructure in the chilled zone, suggesting direct crystallization of the peritectic -Cu5Ge phase from a highly undercooled liquid. The Cu-18Ge samples quenched onto a glass substrate as well as those solidified in the drop tube also showed a segregation-free microstructure. An analysis of the nucleation kinetics revealed that the -Cu5Ge phase had a larger nucleation barrier than that of -Cu for all accessible undercoolings. It was suggested that phase selection in the undercooled Cu-Ge liquid might be controlled by transient nucleation kinetics.

• Periodical: Materials Science Forum (Volume 649)
• Pages: 47-52
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.649.47
• Online since: May 2010
• Authors: J.R. Gao, G. Luo, X.H. Luo
• Keywords: Nucleation, Peritectic Alloy, Phase Selection, Undercooling

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