Effect of grain refiner on the tensile and impact properties of Al–Si–Mg cast alloys

• Grain refining of 356 alloys using five types of grain refiners.
• Interaction between the added grain refiner and amount of modifier used (i.e. 30 or 200ppm Sr).
• Role of the added amount of Ti and/or B on the eutectic Si particle characteristics.
• Role of Ti/B on the impact toughness of 356 alloys modified with Sr (30 or 200ppm).

The present study aims to investigate the influence of the addition of Ti and B in the form of five different grain refiners/aluminium master alloys (Al–10%Ti, Al–5%Ti–1%B, Al–2.5%Ti–2.5%B, Al–1.7%Ti–1.4%B and Al–4%B) in conjunction with that of Sr (as modifier) added in the form of Al–10%Sr master alloy to A356.2 alloy. Grain refinement of an A356.2 alloy with Ti and B additions in the ranges of 0.02–0.5% and 0.01–0.5%, respectively, was examined using these different types of grain refiners. Strontium additions of 30 and 200 ppm were made. All alloys were T6-heat treated before mechanical testing. Tensile and impact tests were conducted to evaluate the influence of the interaction between grain refiner and modifier on the mechanical properties. The properties were determined for both the as-cast and heat-treated conditions.

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