Microstructure evolution and strengthening mechanism of A356 composites reinforced with micron and nano SiCp

The single scale SiCp reinforcement has a limited effect on the comprehensive performance of the composite, which restricts the optimization and improvement of its comprehensive performance. In order to improve the material's strong plasticity, wear resistance, thermal expansion and other properties of the comprehensive requirements. The (micron and nano) dual-scale SiCp/A356 composites with different volume fractions were prepared using the combination of powder metallurgy and hot extrusion. The effects of different volume fractions of dual-scale SiCp (15, 20, 25, 30 vol.%) on the microstructure and mechanical properties of A356 composites were studied, and the strengthening mechanism of dual-scale SiCp/A356 composites was analyzed. The results show that with the increasing of dual-scale SiCp content, the distribution uniformity and mechanical properties of SiCp first increase and then decrease. When the content of dual-scale SiCp is 25%, the mechanical properties reach their maximum values, with the hardness, yield strength and tensile strength of 112.3 HBW, 228 MPa and 310 MPa, respectively. They are improved by 86.9%, 81.0%, 74.2% as compared with those of A356 alloy, respectively. The fracture modes of dual-scale SiCp/A356 composites are mainly Al matrix tearing and SiCp fracture. The main strengthening mechanism is Orowan strengthening, along with thermal mismatch strengthening, load transfer strengthening and fine grain strengthening.