NaF-NaCl-KCl-ScF_3熔盐体系中铝热还原Sc_2O_3制备Al-Sc中间合金

Preparation of Al-Sc Master Alloy by Aluminothermic Reduction of Sc_2O_3 in NaF-NaCl-KCl-ScF_3 Molten Salt System

在NaF-NaCl-KCl-ScF3熔盐体系中,采用铝热还原Sc2O3制备出Sc含量0.85%～4.20%的Al-Sc中间合金。引入金属间化合物Al3Sc作为铝热还原Sc2O3反应的生成物,热力学计算结果表明1 093～1 173K温度范围内反应可自发进行,且为放热反应。用等温饱和法测定Sc2O3在NaF-NaCl-KCl熔盐体系中的溶解度,结果表明,提高温度和NaF含量以及添加ScF3均能提高Sc2O3在熔盐中的溶解度,而添加ScF3的效果最显著。考察温度与ScF3添加量对铝热还原过程中Sc回收率的影响。结果表明,温度升高,Sc回收率先提高后降低,在1 133K时达到最大;ScF3添加量增加,Sc回收率亦先提高后降低,在3%ScF3添加量时取得最大值。在1 133K、3%ScF3添加量、保温1.5h条件下得到的Sc回收率最高可达86.06%。对制备的Al-Sc中间合金进行SEM与EDS分析,结果表明,Al-Sc中间合金中存在Al3Sc颗粒,呈方形或多边形,粒径较小,在基体中分布较分散。

Al-Sc master alloys with 0.85%～4.20% scandium content were prepared by aluminothermic reduction of Sc2O3 in NaF-NaCl-KCl-ScF3 molten salt system.Intermetallic Al3 Sc was introduced as a product of Sc2O3 aluminothermic reduction reaction for thermodynamic calculation,and the results reveal that the reaction can spontaneously proceed at 1 013 K～1 173 Kand it is exothermic.Isothermal saturation methods were employed to study the solubility of Sc2O3 in NaF-NaCl-KCl molten salt system.The results show that the solubility of Sc2O3 can be improved by increasing the temperature and NaF content or adding ScF3.Adding ScF3 has the most significant effect.The effects were investigated of temperature and ScF3 addition on Sc recovery during aluminothermic reduction.The results show that Sc recovery increases firstly and then decreases with increased temperature or addition of ScF3,and reaches the maximum at 1 133 Kor with 3% ScF3 addition.The climax of Sc recovery rate is up to 86.06% obtained under the conditions of 3%ScF3addition,1 133 Kand 1.5hisothermal period.The prepared Al-Sc master alloys were analyzed by SEM and EDS.The results demonstrate that there are Al3Sc particles in Al-Sc master alloys,showing square or polygonal shape with small size and dispersed in the matrix.