Q1: How are aluminum alloys classified?
The 4-digit numbering system categorizes alloys:
1xxx: 99%+ pure aluminum (electrical conductivity)
2xxx: Copper alloys (aircraft structural parts)
5xxx: Magnesium alloys (marine applications)
6xxx: Magnesium-silicon alloys (architectural extrusions)
7xxx: Zinc alloys (high-strength components)
Temper designations (e.g., T6) indicate heat treatment processes.
Q2: What makes 6061 alloy widely used?
6061 (magnesium-silicon alloy) offers excellent corrosion resistance and moderate strength (240 MPa yield stress). It's easily weldable and machinable for structural applications. The T6 temper boosts strength through solution heat treatment. Common applications include bike frames, truck bodies, and boat docks. Its extrudability allows complex cross-sections for construction.
Q3: Why is 7075 preferred in aerospace?
7075 (zinc-copper-magnesium alloy) provides exceptional strength comparable to steel. Peak tensile strength reaches 572 MPa when heat-treated to T6 temper. It maintains structural integrity under high stress and fatigue conditions. Aircraft wing spars, missile parts, and landing gears frequently use this alloy. Protective coatings prevent corrosion in demanding environments.
Q4: How does 5052 resist corrosion?
5052 alloy contains 2.5% magnesium for marine-grade corrosion resistance. It forms a stable oxide layer preventing saltwater pitting. The alloy remains ductile at sub-zero temperatures for Arctic applications. Excellent weldability simplifies hull repairs and modifications. Non-magnetic properties prevent interference with navigation equipment.
Q5: What are key thermal properties of aluminum?
Aluminum conducts heat 3-5 times faster than steel (205 vs. 50 W/m·K). Thermal expansion coefficients are twice those of steel (23 vs. 12 μm/m·K). These properties benefit heat exchangers but require expansion joints in structures. Low melting point (660°C) enables energy-efficient casting processes. Alloy selection balances conductivity with mechanical requirements.
