Abstract: This paper presents the effects of different process parameters in producing Al-5Ti-1B grain refiner, i.e. various sequences and reaction time, on grain refinement efficiency of aluminum castings. It was found that different process parameters resulted in different morphology and size distribution of TiAl3 and TiB2 in grain refiner. The experiment was carried out by adding KBF4 and K2TiF6 to molten aluminum. The melting temperature was controlled at 800℃ in an electric resistance furnace. Three different sequences of KBF4 and K2TiF6 additions were applied, i.e., adding KBF4 before K2TiF6, adding K2TiF4 before KBF4 and mixing both KBF4 and K2TiF6 before adding to molten aluminum. Three different holding time at 1 min, 30 min and 60 min were applied. The results showed that no significant difference of morphology and size distribution was found by varying three different sequences. Whereas, the different holding time provided major differences in both morphology and size distribution, which are technically expectable from diffusion and agglomeration between particles resulting in larger particle size and wider range of size distribution of TiAl3 and TiB2. If the reaction time was longer than 30 min, morphology of both TiAl3 and TiB2 became too large. If the reaction time was too short, less reaction between TiAl3 and TiB2 to form would be obtained. For grain refinement efficiency, it was found that mixing KBF4 and K2TiF6 before adding to molten aluminum with a holding time of 30 min resulted in best grain refinement efficiency.

Key words: Grain refinement, Process parameters, TiAl3, TiB2, K2TiF6, KBF4