Effect of La2O3 on the Microstructure and Grain Refining Effect of Novel Al-TiO2-C-XLa2O3 Refiners

Abstract

New aluminum grain refiners, Al-TiO₂-C-XLa₂O₃ refiners, were manufactured by the in situ reaction of Al powder, TiO₂ powder, C powder, and La₂O₃ powder. The effects of La₂O₃ on the refiners’ microstructure and the grain refining effect of the Al-TiO₂-C-XLa₂O₃ refiners on industrial aluminum were studied. The effect of the sintering process was also studied. The results show that the refiners contain Al₃Ti, TiC, Al₂O₃, AlN, and Al₂₀Ti₂La. As the content of La₂O₃ increases, the amount of Al₂₀Ti₂La also increases. However, the amounts of Al₃Ti, Al₂O_3, and TiC decrease. Al₃Ti is a lath-like compound whose size becomes smaller. The distribution of Al₂O₃ and TiC, however, is more uniform. The Al-TiO₂-C-0.2La₂O₃ refiner has the best grain refining effect on industrial aluminum. The size of the industrial aluminum refined by the Al-TiO₂-C-0.2La₂O₃ refiner is 320 μm; the refiner’s grain size is 8.4% that of the industrial aluminum without refiners 0 μm (380). After adding the novel Al-TiO₂-C-0.2La₂O₃ refiner, the nucleation temperature T_N reached 679.21 °C, which is 17 °C above the nucleation temperature of the industrial aluminum without refiners. The primary transformation time is the longest at 25.5 s, which is 4.6 s higher than that of industrial aluminum (20.9 s). Furthermore, the ΔT of the aluminum is 0.5 °C, which is the lowest value.