Effect of B2O3 on microstructures and mechanical properties of cast Mg-Al-Ti-B alloys

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 mu m, 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.