5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

Al-Si alloys, which contains eutectic, are used in large quantities. Those are used not only like cast alloys but for base material of brazing technology as well. It is well known that too long Si lamellae can reduce the joining force of brazing, therefor it is necessary to produce finer eutectic structure. During manufacturing of brazing materials, the use of modifying agent (Na, Sr) is not always permitted. In these cases, we can perform to stir the melt. Eutectic and hypoeutectic Al-Si samples were solidified unidirectionally in a rotating magnetic field of different intensity and the developing structure was investigated. The regular investigation method for these irregular eutectics is the measure of the average distance of eutectic Si lamellae. But this technique is not saying anything about the size of lamellae and about the direction of growing them. Because that we worked out a measuring method by use of mosaic pictures. During our research work it was found that stirring of melt can change the microstructure of the sample radically: primary silicon and primary aluminum appear near each other and the structure of eutectic is very different around the primary phases. The size and the direction of eutectic lamellae were modified by stirring as well. Our study shows interesting effects of magnetic stirring and generate some question about the causes.