Aluminum 7075-T6: Aerospace-Strength Al-Zn-Mg-Cu Alloy — Aircraft Structures & High-Stress Parts

Generally NO — 7075 is considered UNWELDABLE by conventional fusion welding processes. The problem is hot-cracking (solidification cracking) in the fusion zone and liquidation cracking in the partially melted zone of the heat-affected region. The Cu content (1.2-2.0%) widens the solidification range, and the Zn+Mg combines to form low-melting-point eutectic phases at grain boundaries. Friction stir welding (FSW) can successfully join 7075 without melting — this is how SpaceX welds 7075 aluminum-lithium alloy for rocket propellant tanks. For bolted/riveted assemblies (the standard joining method for 7075), specify NAS or MS aerospace fasteners in cadmium-plated alloy steel or A286 CRES for corrosion compatibility.

7075-T6 is significantly stronger (yield: 503 MPa vs 345 MPa for 2024-T3 — +45%) but less damage-tolerant (lower fracture toughness, higher fatigue crack growth rate). 2024-T3 has superior fatigue resistance and is preferred for lower wing skins and fuselage skins where fatigue crack propagation (not static strength) governs the design. 7075-T6 is preferred for upper wing skins (compression-dominated, strength-critical) and internal structure (frames, bulkheads). 7075-T6 is also significantly more susceptible to stress-corrosion cracking in the short-transverse direction — T7351 temper is used when SCC resistance is critical, with a strength penalty of approximately 10-15%.