High Temperature Properties of AZ91D Magnesium Alloy Composite Reinforced with Short Alumina Fiber and Mg₂Si Particle

Abstract

Short alumina fiber- and in situ Mg₂Si particle reinforced magnesium alloy composites were fabricated by squeeze casting. The in situ Mg₂Si particles were formed during the infiltration with the melt into the preforms consisting of the fibers having Si particles attached to their surfaces. The microstructure of the composites and their tensile strength and Young’s modulus in the range from 293 K to 523 K were investigated. The effect of the Mg₂Si particles on the tensile properties was examined by comparison with the properties of the fiber-reinforced composite without the Mg₂Si particles. Fine Mg₂Si particles with a grain size of approximately 5 μm were formed due to the rapid solidification in the permanent mold. The dispersion of the Mg₂Si having a high Young’s modulus was found to be effective for improving Young’s modulus of the fiber-reinforced magnesium alloy composite. The experimental value of the composite was in good agreement with the calculated value based on a previously proposed model. The tensile strength of the composite with 18 vol% fibers and Mg₂Si particles was higher than that of the conventional fiber-reinforced composite at both room temperature and high temperature. Examination of the fracture surfaces indicated that stress transmission between the fiber and the matrix became easy due to the particles, which reduced the fiber-to-fiber contact.