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This paper presents the effects of different process parameters in producing Al-STi-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 TiAl_3 and TiB_2 in grain refiner. The experiment was carried out by adding KBF_4 and K_2TiF_6 to molten aluminum.The melting temperature was controlled at 800℃in an electric resistance furnace.Three different sequences of KBF_4 and K_2TiF_6 additions were applied,i.e.,adding KBF_4 before K_2TiF_6,adding K_2TiF_4 before KBF_4 and mixing both KBF_4 and K_2TiF_6 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 TiAI3 and TiB2.If the reaction time was longer than 30 rain,morphology of both TiAl_3 and TiB_2 became too large.If the reaction time was too short,less reaction between TiAl_3 and TiB2 to form would be obtained.For grain refinement efficiency, it was found that mixing KBF_4 and K_2TiF_6 before adding to molten aluminum with a holding time of 30 min resulted in best grain refinement efficiency.
This paper presents the effects of different process parameters in producing Al-STi-1B grain refiner, ievarious sequences and reaction time, on grain refinement efficiency of aluminum castings. It was found that the different process parameters resulted in different morphology and size distribution of TiAl_3 and TiB_2 in grain refiner. The experiment was carried out by adding KBF_4 and K_2TiF_6 to molten aluminum. The melting temperature was controlled at 800 ° C in an electric resistance furnace. Three different sequences of KBF_4 and K_2TiF_6 additions were applied, ie, adding KBF_4 before K_2TiF_6, adding K_2TiF_4 before KBF_4 and mixing both KBF_4 and K_2TiF_6 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. Here and 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 TiAI3 and TiB2.If the reaction time was longer than 30 rain, morphology of both TiAl_3 and TiB_2 became too large. time was too short, less reaction between TiAl_3 and TiB2 to form would be obtained. For grain refinement efficiency, it was found that mixing KBF_4 and K_2TiF_6 before adding to molten aluminum with a holding time of 30 min resulted in best grain refinement efficiency.