Numerical Simulation and Experimental Studies of Gas Pressure Infiltration Al-356/SiC Composites

In this study, the filling process, solidification parameters, temperature distribution, and residual stress distribution of gas pressure-infiltrated Al-356/SiC composites were investigated through simulation and experiment. In addition, a series of orthogonal tests was also carried out to precisely demonstrate the preheating temperature, infiltration temperature, and infiltration pressure. After a thorough analysis, the orthogonal tests revealed that the optimal process parameters are as follows: the SiC preheating temperature is 550 °C, the infiltration temperature of the Al-356 alloy is 620 °C, and the infiltration pressure is 8 MPa. The simulation results revealed that pressure had a sharp decrease of ~87% during filling, and the critical pressure was ~0.12 MPa. The velocity decreased with the increase in the filling time, and the average velocity was ~2.60 ms−1. Feasible analysis suggested that critical pressure is ~0.11 MPa and average velocity is ~4.20 ms−1; this difference is attributed to apparent velocity and the Kozeny constant. In the solidification process, shrinkage porosity appeared in the centers of the composites, which is evident with scanning electron microscopy. Moreover, the stress concentration of 171.3 MPa appeared in the composite region connected with the runner, which is the cause of the nucleation of the crack. However, based on the optimum orthogonal parameters and simulative results, the stress concentration was reduced, and crack-free and porosity-free composites were achieved.