The microstructures and mechanical properties of a 5vol%SiC/AA2024 nanocomposite fabricated by powder metallurgy

Abstract

A 5vol%SiC/AA2024 nanocomposite was prepared by a powder metallurgy routine involving high energy ball milling (HEBM), spark plasma sintering (SPS) and hot extrusion. The microstructures and mechanical properties of the 5vol%SiC/AA2024 nanocomposite samples prepared using different HEBM and SPS times were investigated in detail. It was found that increasing the milling time from 12 to 24 h caused refinement of Al grains and better dispersion of SiC nanoparticles, leading to a significantly increase of hardness and strength. Increasing the SPS time from 5 to 10 min helped to improve the quality of interparticle bonding, and resulted in grain growth and consequently the formation of a bimodal microstructure which is beneficial for the improvement of ductility. Optimized tensile mechanical properties were achieved in a 5vol%SiC/AA2024 nanocomposite with ball milling time of 24 h and SPS time of 10 min, with its yield strength, ultimate tensile strength and elongation to fracture being 463 MPa, 626 MPa and 4.4%, respectively. Based on the analysis of the contributions of different strengthening mechanisms to the strength, nanoparticle strengthening and grain boundary strengthening made the majority of the contributions to the improved strength of the 5vol%SiC/AA2024 nanocomposite.