Precipitation hardening effect on the aging characteristics of two step stir cast Al7075-GCI_p composites

An investigation into the fabrication and characterization of Al7075-GCIp composites were conducted in this study. Two step, stir casting method was employed for the fabrication of composites with 2, 4 and 6 wt% of grey cast iron particulates (GCIp) of average size 50 microns. Precipitation hardening treatment was given for specimen representing each composition. Aging was carried out at 100, 150 and 200ᴼC for different time periods. Microstructure and experimental study revealthe uniform distribution of reinforcements in the composite with an acceptable level of porosity. This leads to an enhancement in the desirable properties leading to higher hardness. There was an acceleration in the aging process of the composite as the wt% of reinforcements increased. An increase in the number of nucleation sites due to the presence of reinforcement particles resulted in enhanced rates of precipitation. Hindrance for the movement of dislocations due to the presence of fine precipitates increases hardness and strength. As aging at lower temperature gives more number of precipitates, specimen aged at 100ᴼC exhibited higher hardness at each composition with excellent peak hardness for the 6 wt% reinforced composite.