Microstructure and properties of novel Al-Ce-Sc, Al-Ce-Y, Al-Ce-Zr and Al-Ce-Sc-Y alloy conductors processed by die casting, hot extrusion and cold drawing

Abstract

In order to overcome the trade-off between the strength and electrical conductivity of aluminum alloy conductors, the new Al-Ce-Sc, Al-Ce-Y, Al-Ce-Zr and Al-Ce-Sc-Y alloys were prepared by die casting, high temperature homogenization treatment, hot extrusion and cold drawing. Adding Sc and Y eliminated the dendrite segregation of the as-cast Al-0.2Ce alloy and promoted the formation of equiaxed grains with the average grain size of 142.5 μm. The Al-0.2Ce-0.2Sc-0.1Y alloy inherited the great tensile properties of Al-0.2Ce-0.2Sc alloy and the high electrical conductivity of Al-0.2Ce-0.1Y alloy simultaneously. After cold drawing and annealing at 200 °C for 5 h, the ultimate tensile strength of Al-0.2Ce-0.2Sc-0.1Y alloy reached 200 MPa and 198 MPa, the elongation reached 6.8 % and 8.5 %, and the electrical conductivity reached 61.01 % and 61.77 %, respectively. The main second phase of Al-0.2Ce-0.2Sc-0.1Y alloy after hot extrusion were Al₁₃Fe₃Ce containing a few Y and Si atoms. The larger size and proportion of the second phase greatly reduced the concentration of solute Fe and Si atoms and the addition of Y significantly decreased the density of defects after cold drawing compared to Al-0.2Ce-0.2Sc alloy, which improved electrical conductivity of the alloy. Furthermore, the dispersed and coherent nano-size Al₃Sc precipitions of Al-0.2Ce-0.2Sc-0.1Y alloy greatly improved strength, elongation and heat resistance. Compared with Al-0.2Ce-0.2Sc alloy, the lower density of dislocation, stacking fault and subgrain boundary and the larger size of Al₃Sc precipitions with enrichment of Y atoms enable the Al-0.2Ce-0.2Sc-0.1Y alloy to maintain high strength, elongation and electrical conductivity after annealing.