Computational simulation of metal droplet break-up, cooling and solidification during gas atomisation

In an atomisation process for powder production, metal droplets go through undercooling, recalescence, peritectic and segregated solidification before fully solidified. The cooling process is further complicated by droplet break-up during the atomisation. This paper describes a numerical model which combines both cooling and break-up in a single computation. The dynamic history of droplets is solved as discrete phase in an Eulerian gas flow. The coupling between droplet and gas flows are two-way, in which the heat and momentum exchanges affecting the gas flow are treated as source/sink terms in the fluid equations. The droplet models were employed a gas atomisation process for metal powder production and good agreement is achieved with the results in open literature. The model results further confirm that thermal history of particles is strongly dependent on initial droplet size. Large droplets will not go through undercooling while small droplets have identifiable stages of undercooling, unclearation and recalescence. The predictions demonstrate that droplets have very similar profiles during gas atomisation and the major factor influencing the atomisation and solidification process of droplets are in-flight distance.