Abstract:The influence of solution treatment on the microstructure and properties of Mg₂Si/AZ91D composites fabricated from Mg−SiO₂ system via in-situ processing method was investigated. The results show that coarse Chinese script shape Mg₂Si phases can be formed by adding SiO₂ into AZ91D magnesium alloy with Si content up to 1.5% of the alloy melt. During solution treatment, the morphology and distribution of the coarse Chinese script shape Mg₂Si phases are modified. Meanwhile, the β-Mg₁₇Al₁₂ phase is dissolved into the magnesium matrix. With increasing holding time, the coarse Mg₂Si phases tend to dissolve, break and spheroidize. After solution treatment at 420 °C for 16 h, Mg₂Si phases become the finest and relatively well-distributed phase. The tensile strength and elongation are increased by 14.9% and 38.9%, respectively. It is believed that the Mg₂Si phases continuously dissolve and break, and finally the spheroidized Mg₂Si particles are obtained due to the interface tension of Mg₂Si/Mg interface.

Key words: Mg₂Si/AZ91D composites; solution treatment; spheroidized Mg₂Si particle; interface tension