Improving the microstructure and properties of recycled 6061 direct chill casting alloy by Al–Sr-RE modification

Recycled aluminum exhibits significant advantages in reducing energy consumption and CO 2 emissions compared with primary aluminum. However, its application is constrained due to the performance loss caused by high impurity content. This paper investigated the effects of recycled scrap ratio and Al-Sr-RE composite modification on the microstructure and mechanical properties of direct chill (DC) casting 6061 aluminum alloy. The results show that Al-Sr-RE modification transforms needle-like Fe-rich phases into granular and skeletal-like morphologies, significantly improving their roundness and distribution homogeneity. With trace Al-Sr-RE addition, the number of crack initiation sites in the 80 % scrap ratio alloy was reduced. And its elongation and tensile strength are comparable to 65 % scrap ratio alloy. Notably, the radial mechanical property discrepancies in the DC ingot were mitigated since Al-Sr-RE modification improved the microstructural homogeneity of the as-cast alloy. This paper provides a novel approach for mitigating the deleterious effects of impurities and facilitating high-quality production of high-proportion recycled Al-Mg-Si alloys.