Effect of scandium on structure and hardening of Al–Ca eutectic alloys

• DOI: 10.1016/j.jallcom.2015.05.155
• Publication Date: 2015-06-19T13:25:14Z
• Authors: N.A. Belov; E.A. Naumova; A.N. Alabin; I.A. Matveeva
• Keywords: 0205 materials engineering; 02 engineering and technology

Abstract The phase composition, structure and hardening of alloys in the aluminium corner of the Al–Ca–Sc system were studied in the range up to 10% Ca and up to 1% S≿. The experimental study (optical, scanning and transmission electron microscopy with electron-microprobe analysis, differential thermal analysis and hardness measurements) was combined with Thermo-Calc software simulation for the optimization of the alloy composition. It was shown that only phases of the binary systems (Al 4 Ca и Al 3 Sc) might be in equilibrium with the aluminium solid solution. It was shown that the (Al) + Al 4 Ca eutectic had a much finer structure as compared with the Al–Si eutectic, which suggests a possibility of reaching higher mechanical properties as compared to commercial alloys of the A356 type. The influence of the annealing temperature within the range up to 600 °С on the structure and hardness of the Al–Ca–Sc experimental alloys was studied. It was determined that the maximum hardening corresponded to the annealing at 300 °С, which was due to the precipitation of Al 3 Sc nanoparticles with their further coarsening. With an example of an Al-7.6% Ca-0.3% Sc model experimental alloy, a principal possibility of manufacturing aluminium casting alloys based on the (Al) + Al 4 Ca eutectic was demonstrated. Unlike commercial alloys of the A356 type, the model alloy does not require quenching, as hardening particles are formed in the course of annealing of casting.