THE EFFECT OF ALLOYING ADDITIVES AND PROCESS PARAMETERS ON THE SOLIDIFICATION CHARACTERISTICS OF THE ALUMINIUM ALLOY AlSi7Mg0.3

Abstract

We have investigated the aluminium alloy AlSi7Mg0.3, which is used in the production of castings. Melting was carried out in an electric resistance furnace. Casting was done into measuring cells with thermocouples for simple thermal analysis. Six samples that differed in terms of the additives used for grain refinement and inoculation, with two different holding times, were cast. An alloying material AlTi5B1 was used for grain refinement. The inoculation effect on the solidification was studied with the addition of the inoculant AlSr10. The temperature of the melt in the furnace was 750 °C and the melting time was one hour and ten minutes. Firstly, the samples were cast, the melt was cooled, solidification occurred and finally it was cooled down in the solid state. During the entire cooling process, the temperature as a function of time was measured and the cooling curves were obtained. After the casting, samples for metallographic inspection were prepared. The cooling curves show that in samples with a longer holding time, the additions of either the inoculant or the grain refinement agent, had a better effect. This is evident with a higher maximum liquidus temperature TLmax in sample Ti10 and lower maximum eutectic temperature TE1max in sample Sr10 in comparison to the basis alloy. The same we can conclude from the microstructure analysis of the samples. The samples with inoculant and with a longer holding time, possessed a finer eutectic structure (αAl+βSi), than the samples with the shorter holding time. The same applies for the samples with grain-refinement additions. The estimated grain sizes were smaller in the sample with the longer holding time.