Large undercooling, rapid solidification, and nucleation mechanism during multistage atomisation

Abstract

The large undercooling and rapid quenching that can occur during multistage atomisation are studied both theoretically and experimentally. Results show that these two effects are closely related to and promoted by each other. The level of undercooling for droplets is dependent on alloy composition, powder particle size, and atomisation condition. The cooling rates of droplets depend heavily on their particle size. Both experiments and theoretical analysis on Sn-Pb alloys reveal that a certain function of undercooling has a linear relationship with the logarithm of the mean powder particle particle size. Based on the present results, a mechanism of nucleation preferred on surface oxide is proposed to give a quantitative interpretation of the experimental observations.