International Journal of Metalcasting, 2023 (SCI-Expanded)
In order to further improve the properties of the A356 (Al–7Si–0.3Mg) alloy, which is widely used due to its excellent properties, the effect of alloying different elements has been studied. Recently, the effect of rare earth elements on a-Al grain size and Si morphology, which play a fundamental role in determining the mechanical properties, has attracted attention and studies have focused on this area. Therefore, the effects of the addition of rare earth elements erbium (Er) and europium (Eu) to the A356 alloy at different ratios on the microstructure and mechanical properties of the as-cast and T6 heat-treated condition are investigated in this paper. Grain refinement with the addition of Er and grain coarsening with the addition of Eu were observed. The average grain size decreased by 32% and became 643 µm. On the other hand, the grain size coarsened 36% (873 µm) with the addition of 0.3 Eu to 0.3 Er wt%. The unalloyed as-cast eutectic Si length was 12.0 µm and the Si aspect ratio was 9.6. The acicular long eutectic Si phases had been modified and started to form spherical with T6 state. Although the modification effect on the eutectic Si increases with the increase in the amount of Er, the modification of Eu eutectic Si is much more effective. The most effective eutectic Si modification was achieved by the addition of 0.1 Er + 0.3 Eu wt% with heat treatment when the eutectic Si refined by 80%. The best mechanical properties were obtained with the addition of 0.1 Er with T6 state. In microstructure and fracture surface SEM analysis results, the number and size of intermetallic phases increased with the addition of alloying element. Although these acicular intermetallic phases are reduced in size by heat treatment, they were not fully spherical.