Supersolidus liquid phase sintering of Al6061/SiC metal matrix composites

Abstract

The aim of the present work is to study the effect of reinforcement content and sintering temperature on the densification and microstructural development during sintering of Al6061/SiC composite compacts. Prealloyed Al6061 powder was mixed with various amounts of SiC particles up to 27 vol.-% and compacted at 350 MPa. Sintering was carried out in a dry nitrogen atmosphere at 580–620°C. It was shown that the presence of SiC particles retards the densification of the prealloyed powder during solid phase sintering and liquid phase sintering. This effect is particularly noticeable at SiC fractions higher than ∼9 vol.-%, at which continuous networks of the hard particles are formed. Increasing the sintering temperature to form more liquid phase above the solidus temperature of the aluminium alloy reduces the detrimental effect of SiC particles. It was shown that the reinforcement particles are relatively uniformly distributed throughout the aluminium matrix and consequently, better mechanical strength is only achieved at low SiC contents. In fact, formation of SiC clusters during processing greatly reduces the mechanical strength of Al6061/SiC composites produced by a powder metallurgy route.