Production of Rapidly Solidified Aluminium Alloy Powders by Gas Atomisation and Their Applications

Light engineering alloys based on aluminium have been the subject of a great deal of attention in the field of rapid solidification processing. As a parallel activity, considerable research effort has been expended on the process of gas atomisation. Understanding of the process has improved, and the influence of processing parameters and nozzle design has been clarified. Results of recent research are reviewed in the present study. Influence of particle size on cooling rates is examined for various atomising gases, and a pilot plant gas atomiser for research into atomisation and for producing research quantity powders is described. Formation of particles and breakup of liquid in atomisation are discussed and related to the distribution of particle sizes in the powder. It is shown that for efficient powder production correct design of the atomising nozzle is of paramount importance. This is explained in terms of supersonic gas flow patterns in the atomising jet, and of the interaction between the gas jet and the liquid metal. The influence of metal temperature, nature and pressure of the atomising gas, production rate, and the level of oxygen in the gas is outlined and related to the particle formation mechanism. Alloy development is reviewed with particular reference to aluminium-transition metal systems for high temperature applications, as well as Al–Li based low density high strength alloy systems and metal matrix composites made from aluminium alloy powder matrix. PM/0511