Spinodally decomposed patterns in rapidly quenched Co–Cu melts

Abstract

The Co–Cu system is analyzed in the region of the metastable miscibility gap with separation of the undercooled melt into the Co-rich and Cu-rich liquids. Phase separation of undercooled and quenched samples of the Co50Cu50 melt are investigated experimentally usingnan electromagnetic levitation technique, quenching on a Pb-solder-coated copper chill substrate and splat-quenching methods. It is found that quenching of the liquid samples with cooling rate J106 K s1 leads to a freezing of splats having the microstructure of spinodally decomposed liquids. The composition of the Co-rich phase measured by transmission electron microscopy is Co71.7Cu28.3 and that of the Cu-rich phase is Co26.8Cu73.2. These compositions are inside the spinodal region and close to the calculated spinodal boundary in the phase diagram of the Co–Cu system at temperatures below T  1450 K. Experimental results are compared with predictions of computational modeling using a model of fast spinodal decomposition.