Aging Kinetics and Microstructural Features of Al6061-SiC+B4C Stir Cast Hybrid Composites

Abstract

The purpose of the current metallurgical work is to analyse the mechanical property alteration and microstructure evaluation of Al6061 hybrid composites by age hardening treatment using three different aging temperatures. Al6061 hybrid composites reinforced with B4C and SiC particles have been manufactured using two-stage stir casting method. The optical micrographs were analysed for the dispersivity of the reinforcements in the matrix. To assure the type of reinforcements in the matrix SEM analysis was carried out. It was found thatduring solutionising and aging at 100, 150 and 200°C, presence of SiC and B4C particles in the hybrid Al6061 matrix composites showed substantial improvement in hardness compared to that of the base alloy. Transmission electron microscopy (TEM) was used to identify the intermetallic phases, morphology and orientation of the particulates responsible for the peak aging behaviour. It was observed that while aging at 100°C excellent peak hardness values are observed in the composite group with well-distributed fine precipitates of Mg2Si along grain boundaries as well as within the grains. The composition Al6061-3B3S composites showed an additional secondary intermetallic phase viz., α-Al12Fe3SiMg along with Mg2Si, which is responsible for the superior aging behaviour over other compositions.