Effects of New Modification and Refinement Techniques of Mechanical Properties and Corrosion Behaviours of Al-Si Alloys

Abstract

In this paper, the effects of new techniques of phosphor-doped elements on the microstructure and mechanical properties of Al-%Si alloy to produce modifier compounds were studied. The modifiers were produced by developing a new technique and additions field (nano- doped metals) under as-cast conditions. The results show that the addition of CuPO4, Ni3(PO4)2 and Ca3(PO4)2 to the Al-Si alloys can change (refine) the primary Si phases and are less angular. In addition, the eutectic Si form has changed from a long needle-like to a fibrous shape. The modified Al-Si alloys have microstructures in the inter-dendrite region consisting of a uniformly distributed α-Al phase, eutectic Al-Si, and fine primary Si particles. The microstructure showed that the primary silicon fraction decreased 60% with increased phosphate elements content. The finest microstructure could be observed with a 0.03% addition of doped metals. Good enhancements in ultimate tensile strength and elongation with clear increases in the hardness were observed, reaching 55%, 9% and 30%, respectively. Moreover, additions give the possibility of changing corrosion behaviours from pitting corrosion to micro and general corrosion. Furthermore, the optimal holding and melting temperature is 780°C, with a holding time of 15 minutes.