SIO2 PARTICLE EROSION OF A356.2 ALUMINUM-ALLOY AND THE RELATED MICROSTRUCTURAL CHANGES

A356-series Al-Si-Mg alloys are subjected to SiO2 sand erosion when th ey are used as the molding die in automatic molding to prepare sand mo ld for casting. In the current investigation, SiO2 sand erosion of the as-cast and T6-treated A356.2 alloy was studied. To simulate the eros ion during the sand-filling process in automatic molding, two test con ditions of about 36 and 66 m s(-1) average particle velocities were ch osen. The results show typical ductile erosion behavior with maximum e rosion rate at oblique impact, although brittle cracking of eutectic S i particles occurs. An ultrafine-grained surface layer which is mixed with fine SiO2 particles can be observed on top of the strain-hardened dislocation cell region. Erosion of the T6 specimens leads to dissolu tion of the Mg2Si precipitates. Owing to this softening effect, the T6 treatment does not improve the erosion resistance. (C) 1997 Elsevier Science S.A.