Mechanical properties of tri-modal Al matrix composites reinforced by nano- and submicron-sized Al2O3 particulates developed by wet attrition milling and hot extrusion

Among all metal matrix composites, aluminum is the most widely used matrix due to its low density coupled with high stiffness. In this study, aluminum matrix composites reinforced by two sizes of alumina particles (35 nm and 0.3 μm) are prepared by wet attrition milling and hot forward extrusion processes. The effect of the ratio of the nano- to submicron-sized particles (2:8, 3:7, 4:6, 5:5, and 6:4 in weight percent) on mechanical properties of the composites is evaluated by micro-hardness and tensile tests. It is found that by increasing the nanoparticles content, the hardness and strength of the composites first increase and then decrease when the amount of the nanoparticle exceeds 4 wt.%. The tensile fracture surfaces are also observed by scanning electron microscopy.