The effect of alloy content on the grain refinement of aluminium alloys

A recent model that predicts the effect of solute content on grain size was shown to predict the effect of titanium additions on the grain size of pure aluminium and an AlSi7Mg0.3 alloy. The model assumes that nucleation on substrates is facilitated by constitutional undercooling in front of a growing grain. To determine how generally applicable the model is to a broad range of aluminium alloys, titanium additions were made to five wrought alloys containing the same level of TiB2. It was found that the grain size obtained is a function of the reciprocal of mc(o)(k-1), the growth restriction factor, and that there is a lower limit to the grain size that can be achieved for the casting conditions used in the experiments, It was also found that at least stoichiometric levels of titanium are required for TiB2 particles to be effective nucleants