Microstructure and Mechanical Properties of Al2O3p/AZ91 Magnesium Matrix Laminated Material Adjusted by Freezing Temperature

Abstract

The Al₂O₃ laminated preforms with different layers thickness were prepared by freezing casting in present work. Then, the Al₂O_3p/AZ91 magnesium matrix laminated materials were obtained by infiltrating the AZ91 alloy melt into the Al₂O₃ laminated preform based on pressure infiltration process. Subsequently, the influence of freezing temperature on the microstructure, mechanical properties and fracture behavior of magnesium-based laminates was investigated. The results indicated that with the decrease of freezing temperature, the thickness of Al₂O₃ layers decreases gradually, the number of layers increases obviously, and the interlayers spacing decreases. Accompanied with the decrease of interlayers spacing, the size of Mg₁₇Al₁₂ phase precipitated in the AZ91 alloy layers was refined, and the compression strength and strain were both improved obviously. The micro-cracks initiated in Al₂O₃ layers during loading process, while the AZ91 layers could effectively suppress the initiation and propagation of micro-cracks. Furthermore, the changing layers structure influenced by the decrease of freezing temperature had significant inhibiting effect on the initiation and propagation of micro-cracks, which endowed the Al₂O_3p/AZ91 magnesium matrix laminated materials with better strength and toughness. Notably, the best compression properties of Al₂O_3p/AZ91 magnesium matrix laminated materials could be obtained at the freezing temperature of − 50 °C, the compression strength and elastic modulus of which were the 160% and 250% of monolithic AZ91 alloy, respectively.