The 7xxx series aluminum alloys are widely referred to as “aerospace-grade” due to their high strength-to-weight ratios. 7075 T651 aluminum is especially sought after because its alloying elements (5.1-6.1% Zn, 2.1-2.9% Mg, 1.2-2.0% Cu) increase strength and hardness while enhancing fatigue resistance.
The T651 classification means that the alloy has undergone solution heat treatment followed by artificial aging and stress relieving, to evenly distribute alloying elements, raise hardness, and reduce distortion during machining.
Machinability of 7075 plate, sheet, and rod is excellent. Cutting forces are low, and the alloy creates small, easy-to-handle chips. It’s even possible to mill surfaces as smooth as 16 μin Ra.
Limitations of 7075 T561 are moderate corrosion resistance and very poor weldability. The alloy is susceptible to pitting and stress-corrosion cracking and should not be exposed to saltwater. Welding, while possible, is not recommended, as it is prone to cracking, and arc heat destroys the benefits of the T651 treatment.
While 7075 aluminum rod, sheet, and plate are used extensively in aerospace, they’re also popular for other demanding applications, ranging from industrial automation equipment to motor-racing components.
| Property | Value | Notes |
|---|---|---|
| Material Type | Aluminum alloy | UNS A97075 |
| Density | 2.81 g/cm3 | 0.102 lb/in3 |
| Melting Point | ~477-635 °C | ~890-1,175 °F |
| Hardness (Brinell) | ~150 | |
| Tensile Strength | ~ 572 MPa | ~83,000 psi |
| Yield Strength | ~ 503 MPa | ~ 73,000 psi |
| Elongation at Break | ~ 11% | T6 treatment reduces ductility |
| Modulus of Elasticity | ~71.7 GPa | ~10.4 x106 psi |
| Corrosion Resistance | Moderate; susceptible to pitting and stress-corrosion cracking | T651 has better stress corrosion resistance than T6 |
| Magnetism | No | |
| Heat Treatment | T651 entails solution heat treatment, artificial aging, and stress relieving | |
| Machinability | Excellent | |
| Weldability | Poor | Welding destroys the benefits of T651 treatment |
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