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

Abstract

New aluminum grain refiners, Al-TiO 2 -C-XLa 2 O 3 refiners, were manufactured by the in situ reaction of Al powder, TiO 2 powder, C powder, and La 2 O 3 powder. The effects of La 2 O 3 on the refiners' microstructure and the grain refining effect of the Al-TiO 2 -C-XLa 2 O 3 refiners on industrial aluminum were studied. The effect of the sintering process was also studied. The results show that the refiners contain Al 3 Ti, TiC, Al 2 O 3 , AlN, and Al 20 Ti 2 La. As the content of La 2 O 3 increases, the amount of Al 20 Ti 2 La also increases. However, the amounts of Al 3 Ti, Al 2 O 3, and TiC decrease. Al 3 Ti is a lath-like compound whose size becomes smaller. The distribution of Al 2 O 3 and TiC, however, is more uniform. The Al-TiO 2 -C-0.2La 2 O 3 refiner has the best grain refining effect on industrial aluminum. The size of the industrial aluminum refined by the Al-TiO 2 -C-0.2La 2 O 3 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-TiO 2 -C-0.2La 2 O 3 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 ∆T of the aluminum is 0.5 • C, which is the lowest value.Many researchers have refined aluminum alloys by adding rare earth (RE) [17,18]. Zhang et al. discovered that a Al-Ti-C-Ce master alloy can refine industrial aluminum effectively [19]. Shi et al. proved that erbium (Er) can refine Al-Si-Mg alloys [20]. However, studies on RE oxides have mostly focused on the preparation of catalysts and glasses [21,22], but the application of RE oxides in the synthesis of Al-TiO 2 -C grain refiners has been less researched.Computer-aided cooling curve analysis (CA-CCA) is often used to characterize the solidification parameters of metals during solidification. Due to its ease of use and low cost, it is the most popular thermal analysis technique [23][24][25]. Farahany et al. used CA-CCA to study the grain refining effect of Sb, Bi, and other elements on Al-Si alloys [26]. Osvaldo et al. studied the solidification process of Al-Cu alloy by CA-CCA [27]. In this paper, novel Al-TiO 2 -C-XLa 2 O 3 refiners were prepared via an in-situ reaction (where X is the weight fraction of La 2 O 3 , equal to 0, 0.1, 0.2, 0.3, and 0.4, as used in this study). The influence of La 2 O 3 on the microstructures of refiners was analyzed. Then, adding different refiners to industrial aluminum, the grain refining effect of refiners on industrial aluminum was studied by CA-CCA. The influence of La 2 O 3 in the sintering process is also discussed. Materials and MethodsIn this experiment, La 2 O 3 powder (purity 99.9%, particle size 5 µm, Baotou Research Institute of Rare Earths, Baotou, China), Al powder (purity 99.9%, particle size 40-50 µm, Beijing General Research Institute of Nonferrous Metals, Beijing, China),...

Effect of Er2O3 on the Structure and Refinement Effect of Al–TiO2–C Refiner

“…With the increase of the test temperature and the large amount of heat released by the reaction, Er 2 O 3 will react with the remaining C powder in the sample and O 2 in the air to form ErC 2 phase, but it is found through calculation that the reaction () Gibbs free energy Δ G = 2 723 915–1552 TJ mol −1 , when Δ G <0, that is, when the reaction can proceed spontaneously, the temperature T is 1755 K (1482 °C). Because reaction () and reaction () will release a lot of heat, [ 12 ] the temperature will rise sharply, which is theoretically higher than the temperature required for reaction (). The transition phase of rare‐earth ErC 2 is not stable at high temperature; it will form TiC and rare‐earth [Er] with free [Ti].…”

“…However, the influence of rare‐earth oxides on the refiner is currently mainly concentrated on La 2 O 3 and Ce 2 O, and other rare‐earth oxides are less studied. [ 11,12 ]…”

Effect of Al-TiO2-C-XY2O3 refiner on grain size and mechanical properties of Al-5Cu alloy

“…Many applications have increasingly demanding material requirements regarding the comprehensive properties of aluminum alloys [1][2][3]. The most effective and economical strategy for improving the comprehensive properties of aluminum alloys is to add a grain refiner to the aluminum alloy melt [4]. At present, Al-Ti-B refiners are usually used in industry to refine aluminum alloys.…”

Fluoride Leaching of Titanium from Ti-Bearing Electric Furnace Slag in [NH4+]-[F−] Solution

“…Titanium dioxide is an irreplaceable high-grade functional white pigment and widely used in coatings [1], rubber [2], papermaking [3], printing [4] and other chemical industries [5][6][7][8][9][10], due to its characteristics, stable chemical properties, good color covering capability, high tinting strength and dispersion, nontoxicity, and electronic properties. Its application is a key indicator for evaluating the national modernization [11].…”