Microstructure and mechanical properties of friction stir welded AA6061/AA6061 + 40 vol% SiC plates

Abstract

The feasibility of butt friction stir welding (FSW) of a metal matrix composite (MMC) with a very high SiC particle content to a monolithic aluminum alloy is tested in this work. It is demonstrated for the first time that sound FSW joints can be obtained between an AA6061 aluminum plate and a thick MMC plate consisting of AA6061 reinforced with 40 vol% SiC particles. The joints withstand tensile testing, with ductile failure taking place in a soft region of the heat-affected zone on the alloy side. Metallographic examination of the MMC side after FSW reveals curved bands, where both the frequency of SiC particles and hardness are significantly lower than those in any other region on the MMC side. It is suggested that these bands are produced by transporting the alloy material to the MMC side, where the alloy is mechanically mixed with the MMC.