Characterization of centrifugally atomized Al-12Si-5Fe-3Cu-1Mg(wt%) alloy powder and extruded rod

Abstract

The Al-12Si-5Fe-3Cu-lMg(wt%) alloy was rapidly solidified by centrifugal atomization. The microstructural characteristics of rapidly solidified powder and the microstructure changes with heat treatment were investigated in terms and related to powder size. The microstructures of the powder consisted of dendritic a-Al, eutectic phase, Cu-rich phase, and needle-like intermetallic compounds. These phases were much finer than that of ingot cast structure and the size decreased with increasing cooling rate. The X-ray diffraction of the atomized powders revealed the presence of non-equilibrium S-(AIFeSi) intermetallic phase. This phase appeared to transform to an equilibrium -(AlFeSi) phase by heating at temperatures above 470°C. The extruded rod which was hot extruded at 360 0 C with an extrusion ratio of 40:1 also revealed the presence of the P-(AIFeSi) intermetallic phase. Using DSC, the exothermic peak due to precipitation from the supersaturated a-Al matrix was observed in the range of 200-250 0 C during continuous heating of atomized powder, and the size of the peaks increased with decreasing powder size.