Effects of variables on size and characteristics of gas atomised aluminium powders

A gas atomisation unit was designed and constructed using free fall liquid metal delivery and a Mannesmann type nozzle. Nozzle geometry, liquid metal flowrate, gas type, and pressure were varied and the effects of these variables on powder mean size, powder morphology, and cooling rate were investigated. Powders with mean size d50 as low as 20 (mu)m were obtained. Powders with mean size d50 greater than 20 (mu)m had irregular shapes and cellular-dendritic structures; smaller powders had spherical shapes and smooth surfaces.