Production of Al-Ti-B master alloys from Ti sponge and KBF4

It is of great interest to replace the K2TiF6 salt so as to reduce the volume of fluoride-bearing particulate material to be added to the aluminium melt in the popular "halide salt" process. Ti sponge was used in the present work as the source of Ti in the production of an AI-5Ti-1B grain refiner. Addition of Ti granules into molten aluminium, either premixed with or before KBF4 salt, has produced Al-5Ti-IB alloys where the boride particles were relatively few and predominantly of the AlB2 type. The grain refining efficiency of these alloys were far from satisfactory. TiB2 was the dominant boride phase with sufficient number of blocky aluminide particles when Ti, in excess of the TiB2 stoichiometry was supplied before and and the balance was reserved for co-addition with KBF4. Al3Ti particles were generated soon after the Ti solubility limit was exceeded in the first step while the boride particles were subsequently produced by the reaction between molten aluminium, KBF4 and K2TiF6. The Al-5Ti-1B master alloy thus produced provided an adequate grain refining performance while the amount of particulate material to be added to the aluminium melt was reduced by nearly 30%. (c) 2006 Elsevier B.V. All rights reserved.