Effect of copper content on microstructure and mechanical properties of Al/Sip composites consolidated by liquid phase hot pressing

Abstract

Aluminum (Al)-based composites reinforced with 50wt.% silicon (Si) were prepared by liquid phase hot pressing. Elemental copper (Cu) powder was mechanically mixed with gas-atomized AlSi alloy powder to form partial liquid phase during sintering, and its effect on densification, microstructure and mechanical properties was investigated. The results indicate that the amount of precipitated Al2Cu (θ) phase increases gradually as the Cu content increases from 0 to 2wt.%. Accordingly, it promotes solid solution hardening along with precipitation hardening, and leading to an enhancement of mechanical properties. However, the presence of too much brittle Al2Cu phase and large Si phase caused by SiSi clustering in the Al-4wt.%Cu/Sip composite debase the mechanical properties remarkably. Cu addition reduces the melting point and results in the formation of Al2Cu phase, thus reducing the consolidation temperature and enhancing the strength of Al matrix. Therefore, the addition of minor elemental Cu powder is an effective approach to promote the preparation and the performance of Al/Sip composites by powder metallurgy.