Surface morphology and microstructure of rapidly solidified Al-base pre-alloyed powders using rotating disk atomization process

It is often desired to control the shape and surface morphology of powders as well as the microstructure of powders. A rotating disk atomization method has been used to produce Al-base pre-alloyed powders with controlled powder shape and microstructure. The characteristics of the powders have been investigated with respect to particle shape, surface morphology, microstructure, hardness and lattice constant of Al phase, α-Al, of the powders. The surface morphology of the powders is significantly influenced by alloy compositions. Although the shape of high purity Al powder is spherical, the coarse shrinkage cavity exists on the surface. The cavity diminishes by addition of 1 wt% Si into the high purity Al. The cooling rates of the powders are estimated to be 105-104 K/s for the particle size less than 100 μm in diameter from the size of the microstructures of Al-33Cu and Al(5N)-1Si pre-alloyed powders. The lattice constant of Al phase, α-Al, decreases and the hardness increases in Al(5N)-1Si pre-alloyed powder as a function of rapid solidification rate. These changes are caused by supersaturation of Si into Al.