Optimum Heat Treatment Processes of SiCp/Al-20Si-4.5Cu Gradient Composites Prepared by Spray Deposition

A SiCp/Al-20Si-4.5Cu gradient composite was prepared by spray deposition and densification technologies, and different solid solution and aging heat treatments were completed. The optimum heat treatment process was obtained by hardness comparing, and then the samples before and after heat treatment were tested by tensile testing and tensile fracture morphology was observed. The results show that the optimum solution temperature of the composite was 485 ℃, the solution time was 1.5 h, the aging temperature was 175 ℃ and the aging time was 7 h. The gradient change of aging rate for the composite was resulted from that of SiC content. The surface layer with the high SiC content exhibited the highest strength of 432 MPa and the elongation of 5.8% in the peak-aged state, and the composite along SiC content gradient lower direction was in under-aged state and exhibited better plasticity. The surface layer with high SiC content exhibited obvious brittle fracture feature, while the layer with the lower SiC content along the gradient direction demonstrated more dimples, enhanced the trend of ductile fracture characteristic.