Effect of Nucleant Particle Size Distribution on the Grain Refining Efficiency of 7xxx Alloys

To refine the as-cast grains of aluminium alloy products, the industry uses grain refiners of different natures, Al–Ti–B or Al–Ti–C. It is commonly known, that depending on their nature, grain refiners have different nucleant particle size distributions. In this work, we highlight the presence of significant differences in particle size distributions in grain refiners of the same nature depending on the producer, but also inconsistencies within production batches from the same manufacturer. We demonstrate the importance of the grain refiner nucleant size distribution on the grain refiner efficiency for aluminium alloys by means of SEM analysis and grain refiner casting tests. Based on our results, we emphasise the necessity of controlling the nucleant particle size distribution to assure grain refiner efficiency.