Relationship between cooling rate and SDAS in liquid phase separated metastable Cu–Co alloys

Cu-50 at% Co and Cu-68.5 at% Co metastable monotectic Cu–Co alloys have been rapidly solidified in a 6.5 m drop tube facility under nitrogen atmosphere. Microstructural evidences proved that liquid phase separation occurred in the alloys as predicted by the phase diagram of the alloy system. As well as liquid phase separated structures, substantial amount of dendrites were also observed. The resulting undercooled metal powders were sieved into ten size fraction range and the SDAS measurements taken using SEM images. Owing to the large number of liquid phase separated structures in the Cu-50 at% Co alloy, SDAS measurements were taken from six size fractions while in the Cu-68.5 at% Co alloy measurements were limited to three size range due to the fragmented nature of its dendrites as the droplet size fraction reduced. A regression relationship between cooling rate and the experimental SDAS measurements was established and an expression of the type was observed in both of the alloys in which the exponential value (n) is approximately 0.2.