Purification of NaCl-KCl Based Inclusion Removal Flux on A356 Aluminum Alloy Melt and Structure and Properties after Purification

Three inclusion removal fluxes (Flux Ⅰ, Flux Ⅱ, Flux Ⅲ) were prepared by adding 10wt%NaF, 10wt%NaF+2wt%Na₂SO₄+4wt%Na₂CO₃, 3wt%NaF+2wt%Na₂SO₄+4wt%Na₂CO₃+7wt%Na₃AlF₆ into NaCl-KCl based purification flux, respectively, and then were used to purify A356 aluminum alloy melt. The purification effect of different fluxes and the microstructure and tensile properties of the alloy after purification were studied. The results show that all the three inclusion removal fluxes improved the metallurgical quality of the aluminum alloy. The content and size of inclusions in the microstructure after purification were reduced, the hydrogen content in the liquid aluminum decreased, and the tensile strength and elongation of the alloy increased. The purification effect of the flux Ⅲ was the best, and the optimal addition amount was 2wt%; the purified matrix structure consisted of equiaxed grains, and the main fracture mode was transgranular micropore (dimples) aggregate ductile fracture.