Influence of thermo-mechanical treatment of Al-5Ti master alloy on its grain refining performance on aluminium

The grain refining response of aluminium (At) was studied with as cast, rolled and heat-treated Al-5Ti master alloys. The Al-5Ti master alloy was prepared by the reaction of K2TiF6 with molten Al. The results showed that rolled master alloys exhibited better grain refining performance as compared to as cast master alloys. Similarly, heat-treated Al-5Ti master alloys showed improvement in the grain refining performance. The improvement in grain refining efficiency of master alloy on rolling has been attributed to the increased fraction of fine TiAl3 particles due to their fracture during rolling. The mean particle size of TiAl3 decreased with increase in the reduction level of rolling. The results also indicated that the morphology of TiAl3 particles changes from plate like in the as cast condition to blocky type after rolling due to fracture of plate like particles. The improved grain refining efficiency of the master alloy on heat treatment was attributed to the increased volume fraction of TiAl3. (C) 2002 Elsevier Science B.V. All rights reserved.