CNC Machining 7050 (AlZn6CuMgZr) — 7xxx Series Material
7050 aluminum alloy (UNS A97050, also designated AlZn6CuMgZr) is a high-strength 7xxx series alloy developed for applications requiring superior stress corrosion cracking (SCC) resistance and fracture toughness compared to 7075. It is specifically designed for thick-section applications, such as aerospace structural components, where through-thickness properties are critical. The addition of zirconium (Zr) refines the grain structure and improves quench sensitivity, allowing for better property uniformity in sections up to 150 mm thick.
Chemical Composition
The composition of 7050 is optimized to balance strength, toughness, and corrosion resistance. Copper and zinc provide solid-solution strengthening, while magnesium and zirconium form dispersoids that control grain growth.
| Element | Composition Range (wt%) |
|---|---|
| Zinc (Zn) | 5.70 – 6.70 |
| Magnesium (Mg) | 1.90 – 2.60 |
| Copper (Cu) | 2.00 – 2.60 |
| Zirconium (Zr) | 0.08 – 0.15 |
| Iron (Fe) | ≤ 0.15 |
| Silicon (Si) | ≤ 0.12 |
| Manganese (Mn) | ≤ 0.10 |
| Titanium (Ti) | ≤ 0.06 |
| Others (each) | ≤ 0.05 |
| Aluminum (Al) | Balance |
Mechanical Properties
7050 is typically supplied in the T7451 (solution heat-treated, stress-relieved by stretching, and overaged) or T7651 temper. The T7451 temper offers the best combination of strength and SCC resistance for thick sections.
| Property | T7451 (Longitudinal) | T7451 (Long-Transverse) | T7651 (Longitudinal) |
|---|---|---|---|
| Tensile Strength (MPa) | 510 – 550 | 490 – 530 | 490 – 530 |
| Yield Strength 0.2% (MPa) | 440 – 480 | 420 – 460 | 420 – 460 |
| Elongation (%) | 10 – 14 | 8 – 12 | 10 – 14 |
| Hardness (HB) | 145 – 160 | 140 – 155 | 140 – 155 |
| Fracture Toughness KIC (MPa√m) | ≥ 30 | ≥ 25 | ≥ 28 |
CNC Machining Parameters
7050 aluminum is known for its excellent machinability in the T7451 temper. It produces well-broken chips and allows for high material removal rates. The following parameters are optimized for CNC machining of 7050 using carbide tooling.
| Operation | Cutting Speed (m/min) | Feed (mm/rev) | Depth of Cut (mm) | Tool Material |
|---|---|---|---|---|
| Rough Turning | 300 – 500 | 0.30 – 0.50 | 3.0 – 6.0 | Carbide (K10, uncoated) |
| Finish Turning | 400 – 600 | 0.08 – 0.15 | 0.2 – 0.5 | Carbide (K10, polished) |
| Rough Milling | 400 – 600 | 0.15 – 0.30 (per tooth) | 2.0 – 5.0 | Carbide (AlTiN coated) |
| Finish Milling | 500 – 700 | 0.05 – 0.12 (per tooth) | 0.2 – 0.5 | Carbide (DLC coated) |
| Drilling (HSS) | 50 – 80 | 0.10 – 0.20 | N/A | HSS-Co (M42) |
| Drilling (Carbide) | 100 – 150 | 0.15 – 0.25 | N/A | Carbide (TiAlN coated) |
Applications
7050 is the preferred material for structural components in aerospace and high-performance industrial applications where weight reduction and reliability are paramount.
- Aerospace: Wing spars, fuselage frames, bulkheads, and floor beams in commercial and military aircraft.
- Automotive: High-performance suspension components, control arms, and knuckles for racing and luxury vehicles.
- Defense: Missile components, armor plate, and structural brackets for military vehicles.
- Industrial: Mold bases, fixture plates, and precision machine tool components requiring high dimensional stability.
- Custom CNC parts: Precision-machined brackets, housings, and structural fittings for demanding applications.
CNC Machining Tips
Tool Material: Carbide (K10-K20 grade) for general machining; use DLC-coated tools for finishing to reduce built-up edge and improve surface finish.
Coating: AlTiN or DLC coatings are recommended for high-speed operations; uncoated carbide is suitable for roughing at lower speeds.
Coolant: Flood coolant with a water-soluble oil emulsion (5-8% concentration) is recommended. For high-speed machining, mist cooling or minimum quantity lubrication (MQL) can improve surface finish and tool life.
Heat Treatment: 7050 is typically machined in the T7451 or T7651 temper. Stress relieving is inherent in the T7451 process (stretching after solution treatment). For critical components, a secondary stress relief at 120°C for 4 hours may be performed after rough machining.
Surface Finish Tips:
- Use a wiper insert for finish turning to achieve Ra ≤ 0.4 µm.
- For milling, use a high-shear cutter with a positive rake geometry to minimize burr formation.
- Climb milling is preferred to reduce work hardening and improve edge quality.
- For drilling, use a pecking cycle (depth of 2x diameter) to break chips and prevent packing.
Why Choose Professional CNC Machining
Precision CNC machining of 7050 aluminum requires the right equipment, tooling, and expertise. From prototype to production, professional machining services ensure consistent quality, tight tolerances (down to ±0.005 mm), and optimal surface finish (Ra 0.2 µm) for your 7050 components. Proper chip management and coolant selection are critical to prevent galling and maintain dimensional accuracy in this high-strength alloy.
Published: 2025-03-21
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