Aluminum extrusion profiles are manufactured from primary aluminum combined with alloying elements and supplementary materials. The raw material system comprises three core components:
Base Aluminum Materials
- 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.
Alloying Elements
- 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.
Supplementary Materials
- 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).
