Effects of Fast Shot Speed and Wall Thickness on the Microstructures and Mechanical Properties of the High Pressure Die-casting 6061-SiC Composites

In this work, a 6061-SiC composite was prepared using the compound casting method and then processed using a vacuum-assisted high-pressure die-casting technology under fast shot speeds of 1, 2 and 3 m/s, respectively. The effect of fast shot speed and wall thickness on the skin layer, porosities and mechanical properties were studied. The results showed that, with the increase of the fast shot speed, the thickness of the skin layer was decreased significantly. The porosities of the samples were decreased first and then increased with the increase of wall thickness. The pore number in the 4-mm sample was the smallest, while the pore number in the 8-mm sample was the largest, with many large-sized strip shrinkage pores. Under a fast shot speed of 1 m/s, the large-sized pores and the skin layer (~ 0.5 mm) led to the brittle fracture and low tensile properties of the sample. When the fast shot speed was increased to 3 m/s, the defects of the microstructures mentioned above were improved, and the sample’s tensile properties were further improved.