Naveed Ali

This study investigates the influence of Si content (1–4 wt. %) and T5/T6 heat treatments on precipitation behavior, electrical conductivity, and mechanical properties of a Ca-modified high-Mg Al–5Mg–xSi (Almag5–xSi) alloy system. Thermodynamic and kinetic analyses indicate that increasing Si accelerates Mg₂Si precipitation by reducing nucleation barriers, while trace Ca (nominally 0.02 wt.%) promotes heterogeneous nucleation via Al₄Ca/Ca–Si clusters, refining eutectic Mg₂Si from lamellar to fibrous morphology and enhancing intragranular β″ precipitation. TEM–FFT–IFFT analysis confirms that T6 treatment produces dense, coherent β″ (Mg₅Si₆) precipitates, with partial β′ (Mg₉Si₅) formation in Si-rich alloys. Ca modification induces multi-oriented β″ nucleation and suppresses coarsening. The electrical conductivity increases with Si content and is higher after T6, reaching 48.3±0.5% IACS for Almag5–3Si owing to the near-stoichiometric Mg/Si ratio and solute depletion. The yield strength increases with Si, peaking at 361.7±1.5 MPa in Almag5–4Si, while the ultimate tensile strength reaches 368.3±1.3 MPa. The maximum ductility (13.3%) is observed in Almag5–2Si owing to the stable β″ precipitates. Notably, the Ca-modified Almag5–2Si alloy outperformed the Ca-free Al–5Mg–2Si counterpart, showing a superior strength–conductivity–ductility balance due to refined dense β″ precipitation and early β′ formation. Overall, Si and Ca synergistically optimize strength, conductivity, and ductility.

This study investigates the influence of Si content (1–4 wt. %) and T5/T6 heat treatments on precipitation behavior, electrical conductivity, and mechanical properties of a Ca-modified high-Mg Al–5Mg–xSi (Almag5–xSi) alloy system. Thermodynamic and kinetic analyses indicate that increasing Si accelerates Mg₂Si precipitation by reducing nucleation barriers, while trace Ca (0.002 wt.%) promotes heterogeneous nucleation via Al₄Ca/Ca–Si clusters, refining eutectic Mg₂Si from lamellar to fibrous morphology and enhancing intragranular β″ precipitation. TEM–FFT–IFFT analysis confirms that T6 treatment produces dense, coherent β″ (Mg₅Si₆) precipitates, with partial β′ (Mg₉Si₅) formation in Si-rich alloys. Ca modification induces multi-oriented β″ nucleation and suppresses coarsening. The electrical conductivity increases with Si content and is higher after T6, reaching 48.3±0.5% IACS for Almag5–3Si owing to the near-stoichiometric Mg/Si ratio and solute depletion. The yield strength increases with Si, peaking at 361.7±1.5 MPa in Almag5–4Si, while the ultimate tensile strength reaches 368.3±1.3 MPa. The maximum ductility (13.3%) is observed in Almag5–2Si owing to the stable β″ precipitates. Overall, Si and Ca synergistically optimize strength, conductivity, and ductility.