On the Performance of A Novel Grain Refiner in Hyper-Eutectic Al-Si Cast Alloys

The stringent requirements for pollution reduction are pushing the automotive industry towards the employment of lightweight structures and, therefore, aluminium and its alloys play a remarkable role. Al-Si casting alloy with eutectic or hypereutectic compositions are, normally, employed for the production of high performance automotive products such as pistons and engine blocks which have to withstand critical loading conditions (i.e. high temperature, high pressure and corrosive exhaust gases). In metals, adequate mechanical properties can be easily obtained providing that a sufficiently fine grain size is achieved but this is not the case for Al-Si cast alloys where commercial grain refiner developed on the base of the Al-Ti-B ternary system are highly ineffective due to the poisoning effect of silicon on titanium. The performance of a novel grain refiner in the form of powder addition developed at Brunel University, which can efficiently and reliably refine Al-Si alloys, are assessed in this work. Particularly, the effect of the addition of this novel grain refiner on the microstructural features of both binary hyper-eutectic and commercial Al-Si alloys is studied.