Effect of SiC particulate reinforcement on the precipitation hardening behavior of two step stir cast Al 6061 alloy

In this paper, the production and characterization of Al 6061/SiC composites, prepared by using a stir casting method, were investigated. Al 6061/SiC composites containing 2, 4 and 6 wt. percent of SiC were produced; and samples representative of each composition were subjected to age-hardening treatment at aging temperatures of 100°C and 200°C for different intervals of time. The aging behavior and tensile properties of the cast material were studied. Experimental results show that Al 6061/SiC composites having low porosity levels and a good uniform distribution of the SiC particulates in the matrix of the Al 6061 were produced leading to higher hardness, and tensile strength. Presence of SiC particles in Al alloys accelerating the aging process and thus attain to higher strength. These particles provide more sites for the nucleation of fine precipitates. These fine precipitates hinder the movement of dislocation and thus increases hardness as well strength of materials. After aging at 100°C, highest strength can be obtained at longer duration of aging. This has been supported by Transmission Electron Microscope micrographs of the same condition. For aging at lower temperature gives more number of fine precipitates. It was also found that the precipitation kinetics of GP zones in the composite material was accelerated, owing to the heterogeneous nucleation capability of metastable phases on the SiC particles. Nevertheless, the decohesion of the interface between the metal matrix and SiC particles led to the formation of voids which, subsequently, combined to generate the ductile rupture of the metal matrix.