Surface Chemical Inhomogeneity of High-Pressure Die Cast Al-Si Alloys and its Effects on Corrosion Behaviors and Adhesive Bonding Capabilities

摘要

High-pressure die casting of Al-Si alloys is an attractive manufacturing process for light-weight structural components in the automobile industry. The die casting processes usually result in the contamination of casting surfaces due to die lubricants and in the segregation of alloying elements during solidification. In this paper surface chemical compositions of high-pressure die cast Al-Si alloys were determined quantitatively using surface sensitive analysis techniques, with emphasis on the distribution of residual die lubricants and alloying elements. Inhomogeneity of surface chemical compositions and its effects on corrosion behaviors and bonding capabilities were also examined. Better corrosion resistance and adhesive bonding capability were found in the surface regions near the melt-ingate than in the regions away from the melt-ingate. The different corrosion behaviors and bonding properties observed at different locations on the surface of die cast plates can be well explained in terms of the location-dependent surface chemistry which is thought to result from different temperature gradients in the die cavity and cooling rates during solidification processes.