Grain refinement of aluminium by titanium diboride particles : The importance of nucleation, growth restriction, and cooling rate

Abstract: The grain refinement of aluminium by titanium diboride particles, TiB2, using Ti/B grain refiners is common practice in the aluminium industry, but exactly how this grain refinement is achieved is uncertain. Current addition of grain refiner is therefore rarely optimal and excessive addition rates of grain refiner is common. This study investigates grain refinement of aluminium by titanium diboride to create a method and/or model which can be used to aid in addition rate optimisation. The effect of different parameters on grain refinement is the focus and includes cooling rate, properties of the nucleant particles, and growth restriction. A number of experiments using different test methods was applied to investigate this. The study reveals how the parameters investigated affect grain refinement, and how these can be used to optimises grain refiner addition rate. A model aiding in dealing with the varying abilities of nominally identical grain refiners to produce grains is introduced.The conclusion emphasizes the importance of optimising addition rates of grain refiners, for mechanical as well as environmental reasons, and how this can be achieved by changing the investigated parameters.