Minimizing detrimental impacts of β-Fe in Al-Mg-Si alloy by combining thermal and compression processes

• Published in: Materials characterization 2023-04, Vol.198, p.112752, Article 112752
• Main Authors: Li, Quan, Wang, Junsheng, Liu, Xinxiu, Wang, Bing
• Format: Article
• Language: English
• Subjects: High-conductivity; High-strength; Phase transformation; Recycled Al alloy; Thermo-mechanical processing
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2023.112752

When Al alloy is recycled, it will continue to enrich Fe, Si impurities and form coarse plate-like β-Fe upon solidification, which is very detrimental to the conductivity and mechanical properties of the final components. In this study, a multi-object optimization method was developed to achieve the combination of high-strength and high-conductivity of Al-Mg-Si alloys by optimizing homogenization and hot deformation process. The homogenized elongation reached 14%, which is 50.5% higher than the as-cast state at 9.3% simply by increasing the relative α-Fe fraction fα (α/(α + β) %) from 0.56 to 0.81. By inventing two new thermo-mechanical processing paths: route 1 and 2, a superior combination of strength and conductivity has been achieved. The strength and conductivity of route 1 process are 292.04 MPa and 51.10%IACS, respectively, with fα at 85%; for route 2 process, they are 299.26 MPa and 50.66%IACS, respectively, with fα at 96%. That means the transformation from β-Fe to α-Fe is almost complete. Therefore, the quantitative characterization of β-Fe and α-Fe fractions enables the design of Fe tolerable recycled Al-Mg-Si alloys at high strength, high conductivity, and high ductility. [Display omitted] •A multi-object optimization method was developed to achieve both high-strength and high-conductivity.•Recycled Al-Mg-Si alloy processing was optimized by homogenization and hot deformation.•Detrimental impacts of β-Fe in recycled alloys was successfully minimized by new thermo-mechanical routes.•Quantitative characterization of β-Fe and α-Fe has been achieved by SEM/EDS and TEM.•Almost complete elimination of harmful β-Fe was achieved, improving properties of recycled Al up to the same levels as 6101/6201 conductor alloys.