Erosion of Al-Si alloys by molding silica sand

Al-Si cast alloys have been used as the die material in automatic molding to prepare a sand mold for casting, but the erosion behavior of these alloys during the blowing of SiO₂ molding sand is still not well understood. In this study, four Al-Si alloys of different silicon concentrations (0.9 to 16.9 mass%) and A356 alloy (Al-7Si-0.3Mg, in mass%) were chosen as the test materials. Commercial-grade No. 5 molding sand was used as the erodent. The impact angle varied from 15° to 90° with the average particle velocity fixed at about 66 m/s. The results indicate typical ductile erosion behavior with a maximum erosion rate at the oblique impact. Nevertheless, brittle fracture of the Si particles causes the erosion resistance to decrease with increasing silicon concentration. The decrease of the erosion resistance increases with increasing impact angle. Solution treatment to round off the acicular Si particles can improve the erosion resistance. Compared to the other test alloys in the as-cast condition, A356 alloy which contains 0.3 mass% magnesium possesses better erosion resistance.