Aluminum extrusion profiles are manufactured from primary aluminum combined with alloying elements and supplementary materials. The raw material system comprises three core components:
Electrolytic Aluminum : Produced by electrolyzing alumina (Al₂O₃) in cryolite-based baths. High-purity electrolytic aluminum (99.5–99.8%) minimizes impurities, enhancing conductivity, corrosion resistance, and extrudability. Recycled Aluminum : Sourced from scrap (e.g., window frames, cans, automotive parts). While cost-effective and eco-friendly, it may contain trace impurities (Fe, Si), requiring strict quality control to maintain profile integrity.
Silicon (Si) : Enhances fluidity and castability (e.g., 4xxx series). With magnesium, forms Mg₂Si precipitates in 6xxx series alloys (e.g., 6063, 6061), widely used in structural and architectural profiles. Magnesium (Mg) : Key for 5xxx series (e.g., 5052, 5083), improving strength, weldability, and corrosion resistance for marine/automotive applications. Copper (Cu) : Strengthens 2xxx series (e.g., 2024, 2014) via θ-phase (Al₂Cu) precipitates. Reduces corrosion resistance but critical for aerospace components. Manganese (Mn) : Refines grains in 3xxx series (e.g., 3003), boosting toughness and heat resistance for heat exchangers. Zinc (Zn) : Forms high-strength 7xxx alloys (e.g., 7075) with Mg/Cu, ideal for aircraft structures. Secondary Elements : Titanium (Ti) & Boron (B) : Grain refiners (e.g., Al-Ti-B master alloys) that optimize cast microstructure. Zirconium (Zr) : Inhibits recrystallization and enhances thermal stability in high-temperature alloys. Rare Earths (e.g., Sc) : Improve fluidity, reduce inclusions, and refine grains.
Fluxes (e.g., chlorides/fluorides): Remove oxides/hydrogen during melting (e.g., hexachloroethane degassing). Covering Agents : Shield molten aluminum from oxidation (e.g., salt mixtures). Modifiers (e.g., Na/Sr salts): Transform eutectic silicon morphology in Al-Si alloys, enhancing strength. Lubricants (e.g., graphite/grease): Minimize friction during extrusion, improving surface quality. - Key Considerations
Sustainability : Recycled aluminum reduces energy consumption by 95% vs. primary production but requires impurity management. Alloy Selection : Dictates mechanical properties; 6xxx series dominates extrusion (70% of global output) due to balanced strength and extrudability. Purity Standards : Electrolytic aluminum ensures consistency for high-precision applications (e.g., electronics).
