Microstructure and properties of AA7075/Al–SiC composites fabricated using powder metallurgy and hot pressing

Abstract

Solid state recycling of AA7075 chips by hot pressing is a novel processing technique that uses remarkably lower energies compared to conventional recycling by casting. In this study, AA7075 chips were recycled to fabricate SiC particle (2.5, 5 and 10wt.%) and Al powder (10, 20, 30 and 50wt.%) reinforced AA7075 alloy matrix composites by the combination of powder metallurgy and hot pressing techniques. The effects of the amounts of SiC particles and Al powder on the microstructure of the recycling AA7075/Al–SiC composites were investigated. The density, porosity and hardness of the composites were also examined. It was observed that the Al powders in the AA7075/Al–SiC composites were distributed non-homogeneously and randomly between the AA7075 chip regions. The results showed that the green density of the AA7075/Al–SiC composites increased with increasing amounts of Al powder, while SiC showed the opposite effect. The hot pressed density (final density) of the composites decreased with increasing amounts of Al powders and SiC content. An increase in the weight percentage of the SiC particles (from 0 to 10wt.%) in the AA7075/Al–SiC composites improved the hardness of the recycled composites due to the high hardness of the SiC particles.