DEVELOPMENT OF AI-TiC MASTER ALLOYS FOR GRAIN REFINING OF ALUMINIUM ALLOYS

Abstract

Grain refinement of aluminium and its alloy castings through additions of grain refiners has been a common industrial practice. In this work, a number of routes were explored for the synthesis of Al-Ti-C master alloys. Conditions have been established on a laboratory scale for the preparation of AI-Ti-C grain refining alloys by a new method in which direct reaction between liquid aluminium, titanium oxide and graphite is used for synthesis. The composition of the master alloy produced is Al-4%Ti-0.5%C. Not only this but also Al-5%Ti and Al-5%Ti-1%B alloys were also produced using established processing routes. The aim was to compare the efficiency of the Al-Ti-C master alloy produced by this method with that of the already established Al-Ti-B master alloy. The microstructure of the developed alloy was investigated by using optical microscopy, SEM, EPMA and XRD studies. The results are in agreement with those available in literature. The thermodynamic basis of the preparation reaction is also explained. At the same time the thermodynamics associated with Al grain refinement by the addition of Al-Ti-C master alloys are discussed. The effects of the following factors were investigated:-addition rate of each master alloys and the holding time before pouring. The results of grain refinement are promising.