Improved particle dispersion and interface characteristics in AA7075–SiC composites fabricated by a novel carrier-gas assisted reinforcement feeding system

AA7075 Aluminum Matrix Composite reinforced with 2.5 wt.% SiC particles was developed by a novel carrier gas-assisted hollow shaft stir casting method. The results are compared with conventional stir casting. The optical microstructural studies revealed that grain refining is achieved by decreasing the average grain size from 85 μm for conventional composite to 63 μm for gas-assisted composite. The SEM studies revealed that particles are clustered together along with micro-voids for conventional composite, whereas better distribution of particles along with fewer defects are observed for gas-assisted composite. The TEM studies revealed that SiC particles are well-embedded into the matrix along with a stable interface between reinforcement and matrix. The XRD studies revealed that Al is the major constituent of the matrix along with SiC reinforcement. The microhardness is improved from 71 HV for the base metal to 80 HV for conventional composite and 92 HV for gas-assisted composite. The ultimate tensile strength is improved from 180 MPa for base metal to 205 MPa for conventional composite and 235 MPa for gas-assisted composite. The porosity is reduced from 0.7% to 0.3% for gas-assisted stir composite. The proposed method is suitable for developing high-strength lightweight materials for various engineering applications.