Abstract:The Mg-Zn-Y quasicrystal-reinforced AZ91D magnesium matrix composites were prepared by squeeze casting process. The effects of applied pressure on microstructure and mechanical properties of the composites were investigated. The results show that squeeze casting process is an effective method to refine the grain. The composites are mainly composed of α-Mg, β-Mg₁₇Al₁₂ and Mg₃Zn₆Y icosahedral quasicrystal phase (I-phase). With the increase of applied pressure, the contents of β-Mg₁₇Al₁₂ phase and Mg₃Zn₆Y quasicrystal particles increase, further matrix grain refinement occurs and coarse dendritic α-Mg transforms into equiaxed grain structure. The composite exhibits the maximum ultimate tensile strength and elongation of 194.3 MPa and 9.2% respectively when the applied pressure is 100 MPa, and a lot of dimples appear on the tensile fractography. Strengthening mechanisms of quasicrystal-reinforced AZ91D magnesium matrix composites are chiefly fine-grain strengthening and quasicrystal particles strengthening.

Key words: magnesium matrix composite; squeeze casting; quasicrystal; microstructure; mechanical properties