Manufacture of Al-Ti-B master alloys by the reaction of complex halide salts with molten aluminium

The influence of various process parameters, involved during the preparatio n of Al-Ti-B master alloy by the reaction of halide salts with molten alumi nium, on the microstructure and the grain refining behaviour of Al-5Ti-1B m aster alloys has been studied in detail. The results shows that, morphology of Al3Ti strongly influences the grain refinement behaviour of the master alloy. The grain refining efficiency of the present master alloy compares f avourably with the widely used commercial master alloys such as those of LS M and AB. Thermomechanical treatment of as-cast master alloy has resulted i n a better grain refinement due to increased nucleating sites caused by the fracture of Al3Ti and the formation of duplex particles. In addition, the grain refining behaviour of Al-0.2 and 2%Cr, Al-0.2 and 2%Zr and Al-0.2, 2 and 7%Si alloys has been studied in detail with conventional (0.2%) as well as higher addition levels of 5/1 TiBAl. The degree of the poisoning effect appears to decrease in the order of Cr, Zr and Si. Mg can counteract the p oisoning effect of Si. (C) 1999 Elsevier Science S.A. All rights reserved.