The solution treatment In Al-Si system casting alloys is usually performed to obtain supersaturated solid solution and spheroidising Si particles. It can be inferred that a high temperature solution treatment enhances mechanical properties without any special apparatuses or techniques. However, it is well known that the solution treatment close to an eutectic temperature causes local melting. In this study, the change in microstructure of Al-Si-Cu casting alloys, which have been solution treated at temperatures ranging from 773 to 824 K, have been investigated from a viewpoint of Cu concentration and the distributions of micropores and locally melt regions due to eutectic reaction. Tensile and hardness tests were carried out to discuss the relationship between mechanical properties and microstructures. In addition to a surface observation, an internal microstructural observation was carried out using the high resolution X-ray computed tomography. The burnt regions during the high temperature solution treatment were identified to be Cu rich. Porosity increased with increasing the solution treatment temperature. The porosity in the sample solution treated above a binary eutectic temperature was confirmed to be >0-2 vol.-%. The Cu concentration in the α-phase increased below the binary eutectic temperature.
All Science Journal Classification (ASJC) codes