1: Production and properties of master alloys of Al–Ti–B type and their ability to grain refine aluminium

A great number of Al–Ti and Al–Ti–B master alloys have been synthesized, varying parameters such as the order of addition of the alloying elements, the relative and absolute amounts of titanium and boron, the temperature ofaddition, the holding time before cooling, and the cooling rate. The efficiencies of all the master alloys as grain refiners of aluminium were tested and the time characteristics, i.e. the change in grain-refining potency with contact time, determined. The Al₃Ti phase found in the master alloys can develop three different crystal morphologies, depending on the production parameters chosen. The morphology of the Al₃Ti particles seems to influence the time characteristic of the master alloy. The results from the grain-refinement test can be explained neither by boride–carbide theory nor by the peritectic theory.