The fabrication process and mechanical properties of SiCp/Al-Si metal matrix composites for automobile air-conditioner compressor

Abstract

The fabrication process and mechanical properties of SiCp/Al-Si metal matrix composite (MMC pistons for automobile air-conditioner compressor were investigated. The required material properties for automobile air-conditioner compressor pistons are high strength, good wear,resistance and light weight. SiCp/Al-Si MMCs were fabricated by the powder metallurgy process of vacuum hot pressing at a temperature of 540-570 degreesC with 30 MPa followed by hydrostatic extrusion at 500 degreesC with an extrusion ratio of 8:1, The compressor pistons were,made by the one-step forging of extruded bars at 400 degreesC. The tensile strength and hardness of Al-10-12 wt.%Si alloys and 5-10 wt.%SiCp/Al-10-12 wt.%Si MMCs were increased by hydrostatic extrusion and forging, mainly due to a decrease of the grain size in the matrix through plastic deformation. The hardness of SiCp/Al-12 wt.%Si MMC was higher than that of SiCp/Al-10 wt.%Si MMC due to the higher Si content. The wear behavior of SiCp/Al-12 wt.%Si MMC was controlled by the surface hardening and cracking of the matrix, and the wear resistance increased with increase in the weight fraction of SIC particles. On the other hand, the wear behavior of SiCp/Al-10 wt.%Si MMC was controlled by the plastic deformation of the matrix and the wear resistance was almost independent of the SIC particle weight fraction.