Abstract:The Mg-Al-Ti-B alloy prepared by mechanical alloying is poor in microstructural uniformity and compactness. In order to improve the microstructural uniformity and compactness of Mg-Al-Ti-B alloy and thus to improve the mechanical properties, effect of B₂O₃ on microstructure and mechanical properties of cast Mg-9Al-6Ti alloy was studied by optical microscopy, scanning electron microscopy, X-ray diffraction and mechanical property testing. The results show that due to the addition of B₂O₃, the average grain size of Mg-Al-Ti-B alloys is refined to 12 μm, dispersed Ti phases completely disappear, the amount of precipitation phase Mg₁₇Al₁₂ is reduced and TiAl₃ is increased, and new phases MgB₆ and Ti₃B₄ are precipitated. The average hardness, average tensile strength, yield strength and elongation of the alloy are HV 77.1, 171.2 MPa, 113.5 MPa and 5.2%, respectively.

Key words: magnesium alloy; boron trioxide; microstructure; mechanical properties