Influence of processing parameters on microstructure and mechanical response of a high-pressure die cast aluminum alloy

Motor sealing brackets were fabricated by pressurized die casting (PDC) process under 408 MPa pressure via semisolid thick slurry of Aluminum Alloy 6061 base metal and 20% powder-chip of similar composition (average 500 mu m). Initially, 81 microns powder (40% by weight) and micro-size chips (60% by weight) were mixed by stirring near 300 degrees C until the diffusion of powder takes place and then refined by ball milling process. Influence of thick semisolid slurry modified by powder-chip reinforcement was investigated according to unmelted chip distribution inside the formed cavities, reinforcement incorporation factor (RIF), density measurement, blister formation along the surfaces and microhardness. The obtained results reveal that the unmelted particles significantly improved the microhardness value and density as 134.85 HV and 2.71 g/cm(3), respectively, also with the reduction in the size of cavities. Refined microstructures were observed at several locations of the components due to the effect of processing parameters.