The effect of processing conditions on the microstructure and impact behavior of melt infiltrated Al/SiCp composites

In the current research, pressureless melt infiltration (PMI) was applied to study the effect of different processing conditions on the final properties of Al/SiC composites, fabricated through the infiltration of aluminum melt into SiC particulates porous preforms. Charpy impact test was used to explore the impact behavior of the Al/SiC composites, obtained from variable processing conditions. Conducting the process at a higher infiltration temperature (1350 °C) increased the final relative density of composites up to the value of 0.97 of theoretical density (TD). The application of a post sintering procedure in nitrogen atmosphere after the completion of infiltration resulted in a slight increase (∼1) in the final density of composites compared to the only infiltrated ones. Instead, the final density of argon sintered composites has undergone a 0.41% reduction. This can be originated from the occurrence of chemical reactions in the N2 atmosphere resulting in the formation of consequent phases, contrary to the argon neutral gas. Results concerning with the impact resistance demonstrated a remarkable superiority for the impact energy of the composites subjected to the combined infiltration and sintering (MIS) procedure compared to the infiltrated ones. While such an observation was found to be identical through sintering in both atmospheres, the appearance of brittle phases formed through sintering procedure in nitrogen gave rise to higher impact energy for the argon sintered composites.