A computer-aided quality control method for the modification of AlSiL2 melts

This paper deals with a study of sodium modification of AlSi alloys with silicon contents from 9.85 to 13.5%. Several test pieces including derivative thermal analysis (DERTA) samples, test bars for tensile tests and cylinders with different diameters were cast with different degrees of modification. The relationships between the degree of modification, chemical composition and thermal analysis parameters were studied by correlation analysis with a microcomputer. The results show that mechanical properties (the yield strength, the tensile strength and the elongation) increase in general with increasing degree of modification. A correlation between the degree of modification and the temperature of eutectic recalescence was found. On the basis of the results, a computer-aided quality control method was developed based on derivative thermal analysis. The method can be used to predict the degree of modification of AlSi 12-melts prior to casting. The quality control method has been successfully tested in the laboratory as well as in an industrial foundry.