Effect of Na 3 AlF 6 contents in refining flux on 3D characteristics of pore and mechanical properties of recycled Al-Mg-Si alloy

Fluoride is an essential and effective component in solid refining flux due to its ability to dissolve Al 2 O 3 . In this paper, the effects of Na 3 AlF 6 content in refining flux on the pores and mechanical properties of recycled Al -Mg -Si alloy was investigated by tensile testing, scanning electron microscope (SEM) and Synchrotron radiation X-ray computed tomography (SRXCT). The results show that addition of Na 3 AlF 6 transformed the shrinkage pores with large -sized irregular -shaped to highly spherical hydrogen pores, resulting in a significant reduction in pore volume fraction. When the refining flux with 5% Na 3 AlF 6 is added to the melt, the volume fraction and average equivalent diameter of pores in the recycled alloy decreased by 84% and 23.2%, respectively, compared to those flux of without Na 3 AlF 6 . Furthermore, adding Na 3 AlF 6 improves pore distribution uniformity while reducing the equivalent diameter of the largest pore by 83.7%. Although increasing Na 3 AlF 6 content slightly increases pore equivalent diameter, it significantly reduces both larger pores (Equivalent diameter >= 20 mu m) and their proportion. Moreover, the elongation of recycled Al gradually increases with higher Na 3 AlF 6 content and reaches up to 21%, which is 40% higher than that without Na 3 AlF 6 . This improvement can be attributed primarily to reduced size and sphericity of shrinkage pores.