Effect of Some Additions on the Structure and Mechanical Properties of A356 - Al Si Alloy

Abstract

The modified eutectic silicon or refinement of primary silicon particles with uniform distribution are desired in real casting practice. In order to modify the microstructure of Al-Si alloys, many techniques are available. However the deliberate additions of several elements during melting are still the most easy and efficient way than other different techniques. Trace addition of Na or Sr is commonly used to modify the eutectic structure of Al-Si alloys from coarse plate-like structure in unmodified alloys to fine fibrous morphology in modified ones. Such a fine structure can potentially increase the ductility and tensile properties of these alloys. It was concluded that, 7% Si – 0.3% Mg alloys appeared to be a good refiner when treated by the additions of 0.2-0.4% AlTiB master alloy. In the same time, this alloy reaches good modification by the addition of 0.2-0.4 wt % of Al-10% Sr. The obtained results were compared with those obtained by using the traditional well known AlSr master alloy, AlTiB and a mixture of both AlTiB and AlSr.