7050 aluminum plate is an ultra-high strength aluminum alloy of the Al-Zn-Mg-Cu series. It is an improved version of 7075. By optimizing the composition and heat treatment process, it significantly improves stress corrosion resistance and fracture toughness while maintaining high strength, becoming one of the core materials in modern aerospace and military fields.
National standard (GB/T): 7050 (corresponding to the old brand LC4).
American Standard (AMS): AMS 4050, ASTM B247 (aerospace grade).
European standard (EN): EN 573-3 (AlZn6MgCuZr).
ISO standard: AlZn6MgCuZr (ISO 209).
Main component range (mass percentage)
element | Content range (%) | Core role |
Zinc (Zn) | 5.7~6.7 | Main strengthening element (forming MgZn₂ phase) |
Magnesium (Mg) | 1.9~2.6 | Collaborative strengthening to improve timeliness |
Copper (Cu) | 2.0~2.6 | Enhanced high temperature strength and heat resistance |
Zirconium (Zr) | 0.08~0.15 | Refine grains and inhibit recrystallization |
Chromium (Cr) | ≤0.04 | (Replaced by Zr to reduce brittleness) |
Iron (Fe) | ≤0.15 | Strict control of impurities (aviation grade requirements) |
Optimization highlights:
Zirconium (Zr) replaces chromium (Cr) → reduces the tendency of intergranular corrosion and improves toughness.
Copper content is higher than 7075 → better high temperature performance (suitable for supersonic vehicles).
state | Tensile strength (MPa) | Yield strength (MPa) | Elongation (%) | Fracture toughness (MPa√m) |
T7451 (overdue) | 490~530 | 410~450 | 8~12 | 30~35 |
T7651 (overdue) | 460~500 | 390~430 | 10~14 | 35~40 |
T6 (peak effect) | 540~580 | 470~510 | 5~8 | 25~30 |
Features:
T7451/T7651 state: sacrifice 5%~10% strength in exchange for stress corrosion resistance (preferred for aviation structures).
Fracture toughness: significantly better than 7075 (15%~20% higher under the same conditions)
Density: 2.82 g/cm³ (similar to 7075).
Melting point: 480~630℃.
Thermal conductivity: 134 W/(m·K) (slightly better than 7075).
Conductivity: 32% IACS (low conductivity, similar to 7075).
Thermal expansion coefficient: 23.2×10⁻⁶/℃ (20~100℃).
Advantages:
Balance of strength and toughness: The tensile strength of T7451 state is ≥490MPa, and the fracture toughness is excellent.
Resistance to stress corrosion cracking (SCC): After aging treatment, the corrosion resistance far exceeds that of 7075-T6.
High temperature stability: short-term tolerance to 150~200℃ (such as supersonic aircraft skin).
Fatigue performance: The life under cyclic load is 20%~30% longer than 7075.
Limitations:
High processing difficulty: special tools are required (carbide or ceramic tools are recommended).
Very poor weldability: limited to riveting, bolting or friction stir welding (FSW).
High cost: 10%~15% more expensive than 7075 (due to Zr element and strict process).
Aerospace:
Aircraft wing beams and keel beams (key structures of Boeing 777/787).
Space rocket fuel tanks and satellite brackets.
Military equipment:
Armored vehicle turret frame and carrier-based aircraft catapult hook.
High-end industry:
Heavy machinery load-bearing parts, precision molds (requires high fatigue resistance).
(1) Heat treatment process
Solution treatment: keep at 475~490℃ and then quench in water (cooling rate needs to be >200℃/s).
Aging process:
T7451: 120℃×24h + 160℃×8h (corrosion resistance is preferred).
T6: 120℃×24h (strength priority).
(2) Key points of machining
Cutting parameters: low speed (<300m/min), high feed, with emulsion cooling.
Drilling/tapping: Pre-processing annealing state (O state), post-age hardening.
(3) Connection technology
Friction stir welding (FSW): aviation-grade welding, with performance loss in the heat-affected zone less than 10%.
Gluing-riveting composite: used for fuselage skin (such as Airbus A380).
Micro-arc oxidation (MAO): Generates a 50~100μm ceramic layer with salt spray resistance of >3000 hours.
Composite coating: primer (epoxy resin) + topcoat (polyurethane), used for military aircraft skin.
Anodizing: Hard anodizing (HV ≥ 800) improves wear resistance.
