Effect of rotating gas bubble stirring process parameters on purifying effectiveness and mechanical properties of sand-cast Mg-10Gd-3Y-0.5Zr alloy

A continuous nonflux inclusion-removal method, rotating gas bubble stirring, is used to purify Mg-10Gd-3Y-0.5Zr melt. The effects of rotating gas bubble stirring process parameters (Ar flow rate, time, and rotating speed) on purifying effectiveness, mechanical properties, and fracture behavior of sand-cast Mg-10Gd-3Y-0.5Zr alloy are studied. The results show that too high or too low Ar flow rate is unfavorable for inclusion-removal. The results also indicate that the high rotary speed of spraying gas is helpful to improve the inclusion-removal and mechanical properties. But when the melt is subjected to overtime gas bubbling treatment, the mechanical properties became poor again. Nonflux purification does not change the microstructure of Mg-10Gd-3Y-0.5Zr alloy. However, rotating gas bubble stirring has a certain effect on the fracture pattern of the alloy. In addition, the melt purifying mechanism of the gas bubble stirring treatment for the sand-cast alloy was discussed systematically.