Abstract
The rapid solidification of aluminum powder is the most fundamental process in the production of P/M materials. This process must be clearly understood since it directly affects the properties of materials and their production costs. In this study, Al-6Cr-3Fe-2Zr alloy powder, originally developed as a heat-resistant aluminum alloy, has been produced by using two different gas atomization processes involving high- and low- pressure gas atomization, thus enabling more efficient industrial production of powder with a rapid cooling rate. The effects of gas atomization factors on the particle shape, size distribution, surface oxidation and microstructure of the as-atomized particles have been investigated. In addition, these effects on the mechanical properties of materials formed through powder extrusion have been evaluated.
It is found that the particle shape varied with the surface layer of aluminum oxide, which was about 10 nm thick. Atomizing under high-pressure helium reduced the average particle diameter to 18 μm with an excellent size distribution. Particle microstructures largely depend on the particle size and type of the atomizing gas used. The use of helium produced the finest particle microstructure made of Al-Cr-Fe and Al-Zr system dispersoids. The extruded alloy, formed from −25 μm powders which were atomized under high-pressure helium, showed an outstanding tensile strength of 584 MPa at room temperature and 300 MPa at 300°C.
