Influence of hot extrusion on the microstructure and mechanical properties of Al₂O₃/7075 aluminum matrix composites

Abstract

The influence of hot extrusion on the microstructure and mechanical properties of Al2O3/7075 aluminum matrix composites was investigated via optical microscopy, scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, transmission electron microscopy and tensile testing. The results indicate that the yield strength, tensile strength, and elongation of the as-extruded composites respectively reached 244.4 MPa, 360.3 MPa, 11.0 %, which increased by 20.24, 33.28 and 507.73 %, compared to those of the as-cast composites. The hot extrusion process grants the composites fine compactness and significantly improves the distribution of Al2O3 particles in the composite. The eutectic phase at the grain boundaries was crushed into small fragments under shear force after hot deformation. Moreover, high dislocation density near the Al2O3 particles and grain boundaries was observed in the extruded composite. The failure mode of the as-cast material was quasi-cleavage fracture, while the failure mode of the as-extruded material was primarily ductile fracture.