X-ray and optical crystallographic parameters investigations of high frequency induction melted Al-(α-Al2O3) alloys

This article deals with the microstructural strengthening mechanisms of aluminium by means of hard alpha-Al2O3 alumina fine particles. A broad of understanding views covering materials preparations, elaboration process, characterization techniques and associated microstructural characteristic parameters measurements is given. In order to investigate the microstructural characteristic parameters and the mechanical strengthening mechanisms of pure aluminium by hard fine particles, a set of Al-(alpha-Al2O3) alloys samples were made under vacuum by high fusion temperature melting, the high frequency (HF) process, and rapidly solidified under ambient temperature from a mixture of cold-compacted high-pure fine Al and alpha-Al2O3 powders. The as-solidified Al-(alpha-Al2O3) alloys were characterized by means of X-ray diffraction (XRD) analyses, optical microscopy observations and Vickers microhardness tests in both brut and heat-treated states. It was found that the as-solidified HF Al-(alpha-Al2O3) alloys with compositions below 4 wt.% (alpha-Al2O3) are single-phase microstructures of the solid solution FCC Al phase and over two-phase microstructures of the solid solution FCC Al and the Rhombohedral alpha-Al2O3 phases. The optical micrographs reveal the presence of a grain size refinement in these alloys. Vickers microhardness of the as-solidified Al-(alpha-Al2O3) is increased by means of pure fine alpha-Al2O3 alumina particles. These combined effects of strengthening and grain size refinement observed in the as-solidified Al-(alpha-Al2O3) alloys are essentially due to a strengthening of Al by the alpha-Al2O3 alumina particles insertion in the (HF) melted and rapidly solidified alloys.