Effects of Particle-Dispersion on the Strength of an Alumina Fiber-Reinforced Aluminum Alloy Matrix Composite

Aluminum alloy matrix hybrid composites, in which alumina particles were dispersed among continuous alumina fibers, were fabricated by squeeze casting, and the influence of temperature and the effects of the particle-dispersion on the strength of the composites were then investigated. The particle-dispersion among the fibers minimized preform contraction and fiber-to-fiber contact due to the melt infiltration during the squeeze casting. The tensile strength, 0.2 % proof stress and elastic modulus of the composites in the longitudinal direction increased with increasing the fiber volume fraction, retaining nearly the same values up to 623K. These values of the hybrid composite were larger than those of the particle-free composite at every temperature. This is because the fibers were distributed uniformly owing to the particles that prevented the fiber-to-fiber contact, leading to the reduction of stress concentration at the points of direct fiber contact, and stress transmission between the fiber and the matrix becomes easy. At every temperature, the transverse tensile strength and proof stress of the particle-free composite was lower than that of the unreinforced alloy, because the fracture was initiated at the fiber-to-fiber contact point and the cracks propagated mainly along the fiber-matrix interface. In contrast, the strength of the hybrid composite was close to that of the unreinforced alloy even at high-temperature, because the cracks propagated mainly throughout the matrix owing to the uniform distribution of the fibers and the strong fiber-matrix bond