Why 7075 Aluminum is Called Aircraft Aluminum?
When strength matters, 7075 aluminum is the go-to choice. This high-strength alloy is used in aerospace, defense, and racing applications where failure is not an option.
But with great strength comes great machining challenges. Let us explore what makes 7075 special and how to machine it effectively.
What Makes 7075 Different?
7075 is a 7xxx series aluminum alloy with zinc as the primary alloying element. It is one of the strongest aluminum alloys commercially available.
Key Advantages:
- Exceptional strength-to-weight ratio (best among aluminum alloys)
- Excellent fatigue resistance
- Good mechanical properties after heat treatment
- Heat treatable to various tempers
Chemical Composition
| Element | Content (%) |
|---|---|
| Aluminum (Al) | 87.1-91.4% |
| Zinc (Zn) | 5.1-6.1% |
| Magnesium (Mg) | 2.1-2.9% |
| Copper (Cu) | 1.2-2.0% |
| Chromium (Cr) | 0.18-0.28% |
Mechanical Properties (T6 Temper)
| Property | Value |
|---|---|
| Tensile Strength | 572 MPa (83 ksi) |
| Yield Strength (0.2%) | 503 MPa (73 ksi) |
| Elongation at Break | 11% |
| Brinell Hardness | 150 HB |
| Fatigue Strength | 159 MPa |
| Density | 2.81 g/cm3 |
| Modulus of Elasticity | 71.7 GPa |
Strength Comparison: 7075-T6 is nearly twice as strong as 6061-T6!
CNC Machining 7075: Challenges and Solutions
7075 is more difficult to machine than 6061 due to its higher strength and hardness. Here is how to do it right:
Recommended Cutting Parameters:
| Operation | Spindle Speed | Feed Rate | Depth of Cut |
|---|---|---|---|
| Roughing | 2500-4000 RPM | 0.1-0.2 mm/tooth | 1-3 mm |
| Finishing | 4000-6000 RPM | 0.05-0.1 mm/tooth | 0.2-0.5 mm |
Tool Recommendations:
- Solid carbide end mills (mandatory for best results)
- Coatings: TiAlN or AlTiN for heat resistance
- 4-6 flute for finishing operations
- 2-3 flute for roughing and slotting
- Avoid HSS tools (wear out too fast)
Coolant Strategy:
- Use flood coolant or mist lubrication
- Prevent chip welding to cutting edges
- Extend tool life significantly
Common Applications
7075 aluminum is used where strength is critical:
- Aerospace: wing ribs, fuselage frames, landing gear parts
- Automotive: suspension components, roll cages, racing parts
- Defense: firearm receivers, military equipment
- Sports: bicycle frames, climbing gear, baseball bats
- Industrial: high-stress machine parts, molds, dies
Heat Treatment Options
7075 can be heat treated to different tempers:
- T6: Solution heat treated + artificial aging (maximum strength)
- T651: Stress relieved by stretching (better dimensional stability)
- T73: Overaged (better corrosion resistance, slightly lower strength)
- T7351: Overaged + stress relieved
Corrosion Resistance Warning
7075 has lower corrosion resistance than 6061. For harsh environments:
- Apply anodizing or conversion coating (Alodine)
- Consider Alclad 7075 (clad with pure aluminum layer)
- Use protective paint or powder coating
- Consider 7075-T73 for better corrosion resistance
Weldability: Not Recommended
7075 is generally considered unweldable due to cracking susceptibility in the heat-affected zone. For welded assemblies, consider:
- 6061 aluminum (excellent weldability)
- 5083 aluminum (marine grade, weldable)
- Mechanical fastening (bolts, rivets) instead
Why Choose JR CNC for 7075 Parts?
Machining 7075 requires expertise and the right equipment. At JR CNC:
- ✓ Experienced with high-strength aluminum alloys
- ✓ High-speed machining centers (12000+ RPM)
- ✓ Premium carbide tooling (fresh edges)
- ✓ Quality inspection with CMM available
- ✓ Fast turnaround for prototypes and production
Source: ASTM B209, AMS 4045, AMS 4027, ASM Handbook
