Microstructure and Tensile Properties of Mg (AM60)/Al₂O₃ Metal Matrix Composites with Varying Volume Fractions of Fiber Reinforcement

Magnesium alloy AM60 matrix-based composite reinforced with 7, 9, 11, 22, and 35 vol.% of Al₂O₃ fibers was squeeze cast. The microstructure and mechanical properties were investigated in comparison with the matrix alloy AM60. The results of tensile testing indicated that the addition of Al₂O₃ fibers to magnesium alloy AM60 led to a significant improvement in mechanical properties. As the fiber volume fraction increased, the strengths and moduli of the composites were enhanced considerably. However, the notable increase in strengths was at sacrifice in elongation. Microstructural analyses via scanning electron microscopy (SEM) revealed that the grain size decreased with increasing volume fractions of reinforcement. The restriction of grain growth by the limited inter-fiber spacing could be the primary mechanism for a reduction in the grain size of the matrix alloy. The SEM fractography evidently reveals that the debonding of fibers from the matrix alloy and the fiber cracking were two primary mechanisms for the tensile failure of the composites.