Al-Sc Alloy Prepared By Molten Salt Electrolyzing And The Microstructure Analysis

One set of laboratory-used electrolyzer was designed and set up. Pure aluminum, Al-Ti alloy and Al-Sc alloys had been tested and produced using this set of electrolytic cell respectively. We analyzed and dicussed the refinement effect of the Al-Sc alloy and its mechanism in this paper.The magnesium flouride and calcium flouride were added into the cryolite-alumina electrolysis system in the electrolysis experment. According to the problem occurring in the experiment, many steps had been put up and taken into practice in order to maintain the electrolyzing process in order. For example, in order to increase the efficiency of electrolysis, the shape of the cathode was changed from the original rod shape to the disk shape, and the shape of the anode was changed from the tubular shape to the cylindrical shape. In order to solve the fracture of the cathode and anode, the used materials of graphite were changed from the original refined grain to the coarse grain. The low current efficiency and the thermal serious problems. After many improvements, we got a set of electrolzer in easy operation and with high efficiency. And we have used the equipment to produce a kilogram of Al-Sc alloy in once electrolyzing process.The composition of the electrolyzed Al-Sc alloy was analyzed and its micro-structure was determined. The results showed that the electrolysed Al-Sc alloy had obtained refinement much greater than the non-electrolyzed alloy. With the content of Sc increased, the grain refinement effects increased obviously. Contrasted with the electrolysed alloy, the non-electrolyzed alloy, for example prepared by melting, showed in poor refinement, with the uneven distribution of Sc in great segregation. The refinement of Sc to Al alloy is mainly due to the high matching between Al3Sc and Al, their lattice missmatch is less than 1%. Al3Sc to be in line with non-homogeneous nucleation as the structural conditions, and wet well with matrix grain, reduce the contact angle between Al, the surface tension between Al3Sc phase and matrix grains is relatively small, is conductive to the formation of heterogeneous nucleation, the grain refinement purpose can be achieved. The grain area, average diameter, long radius, short radius and radius ratio etc of the electrolyzed Al-Sc alloys were farthermore quantitatively measured and calculated. The grains feature size's change curve with the increase of Sc content, and the probability density distributions of these items were finally made. The results showed that with the Sc content increased, the probability density distribution curve gradually shifted to the left, and the peak tended to increase. The grain size became to smaller, the distribution range was shrinking, and the degree of concentration was increased.