Damping Capacities of Porous Mg-based Ternary Alloys Prepared by a Stir-casting Method

A new approach for preparing porous Mg-Al-Sr ternary alloys has been proposed using stir-casting method. Experimental results indicate that porosity and pore diameters have close relation with chemical composition of Mg-based ternary alloys. The proposed formation mechanism of pores in Mg-based ternary alloys can be described as that the oxidization reaction between [Sr] and O-2 in air provides enough heat source to vaporize small amount of Mg-based ternary alloys, while the vaporized products promote formation of embodied pores with various sizes and shapes in Mg-based ternary alloys during solidification process. Meanwhile, some oxides in shape of sheets will be formed and precipitated, while other oxides will also be precipitated on surface of pore wall during cooling. Moreover, the measured damping capacities expressed by internal friction tan indicate that changing temperature from ambient temperature to 343K cannot cause a large effect on damping capacities, however the inverse V-shape plots of damping capacities against temperature from 343 to 573K are obtained. In addition, increasing vibration frequencies can result in a decrease of internal friction tan. The optimized chemical composition as 50%Mg-47%Al-3%Sr and 50%Mg-45%Al-5%Sr are recommended for Mg-based ternary alloys with greater porosity and higher damping performance under temperature and vibration frequency.