Effects of solution treatment on tensile properties and strengthening mechanisms of SiCp/6061Al composites fabricated by powder thixoforming

Abstract

6061 Al-based composites reinforced with 10% volume fractions of 6.94μm SiC particles (SiCp) have been fabricated by powder thixoforming, and the effects of solution treatment on their tensile properties and strengthening mechanisms were investigated. The obtained results indicate that the addition of SiCp significantly improved the tensile strength of a 6061 Al matrix alloy, but reduced its ductility. The ultimate tensile and yield strengths of the alloy increased from 180MPa and 99MPa to 230MPa and 128MPa, respectively, while its elongation decreased from 8.0% to 2.6%. However, the solution treatment at 535°C for 6h significantly alleviated ductility losses and further enhanced the composite tensile strength; as a result, its ultimate tensile strength, yield strength, and elongation were increased by 19.6%, 65.2%, and 161.5% up to 275MPa, 212MPa, and 6.8%, respectively. Due to the presence of SiCp, the resulting composite solution rate was noticeably decreased compared to that of the matrix alloy. The relationship between the solution time and the composite yield strength was discussed theoretically by using a modified micromechanical model, which took into account the SiCp failure. The obtained theoretical results were in good agreement with the experimental ones.