High-ductility AA6061 alloys produced by combination of sub-rapid solidification and Cr-alloying

Fe-containing phases had a critical influence on the mechanical properties especially the ductility of Al-Mg-Si alloys. In the present study, the Fe-containing phases in Al-1.2Mg-0.7Si-0.1Fe (wt.%, AA6061) alloys had been regulated by the combination of sub-rapid solidification (SRS) and alloying with 0.12 wt.% Cr. Consequently, the coarse needle/platelet b- Al5FeSi phases (average length: ~27 mm) were regulated as polyhedral alpha-AlCrFeSi phases with smaller size (~2 mu m) and uniform distribution. Based on the thermodynamic calculation of solidification paths, this study developed a possible mechanism of the Fe containing phase transformation. Specifically, alloying with Cr accelerated the formation of fivefold symmetry icosahedral quasicrystal 0-Al-13(Fe, Cr)(4) phases (Al13M4 phases), which then combined with Si atoms in the surrounding melt and favored the formation of polyhedral alpha-AlCrFeSi phases. Tensile properties of artificial aged alloys were significantly improved by the combination of SRS and alloying with 0.12 wt.% Cr. The yield and ultimate strength increased from ~254 to ~293 MPa and ~288-~335 MPa, respectively, and the elongation to failure increased from-10% to-21%. This study may provide guidelines to produce high-ductility Al-Mg-Si alloys by optimizing the Fe-containing phases. (C) 2022 The Author(s). Published by Elsevier B.V.