7xxx Series
Aluminum-Zinc Alloys
Overview
Highest strength aluminum alloys, heat treatable, aerospace grade
Stress corrosion cracking susceptible, requires proper heat treatment
Applications
Common Alloys
Properties
Manufacturing Process
Step 1
Material Preparation
High-purity Al combined with Zn (5–8 %), Mg, and Cu master alloys; all materials certified to aerospace traceability requirements.
Step 2
Melting & Alloying
Sequential element additions at 730–760 °C; multi-stage rotary degassing reduces hydrogen to ≤0.06 ml/100g for porosity-free material.
Step 3
DC Casting & Homogenisation
Cast into thick-section billets; 24+ h homogenisation soak at 460–480 °C dissolves Zn-Mg-Cu phases and reduces segregation.
Step 4
Hot Working
Rolled or forged at 380–440 °C through carefully controlled reduction ratios to develop the required wrought microstructure.
Step 5
Solution Treatment & Quench
Solution treatment at 465–475 °C followed by immediate cold-water or polymer quench — quench rate is critical to final strength.
Step 6
Multi-Stage Aging (T73/T76)
Two-step overaging (100 °C + 165 °C) provides resistance to stress corrosion cracking. Extensive tensile, fracture toughness, and SCC testing.
Step 1
Material Preparation
High-purity Al combined with Zn (5–8 %), Mg, and Cu master alloys; all materials certified to aerospace traceability requirements.
Step 2
Melting & Alloying
Sequential element additions at 730–760 °C; multi-stage rotary degassing reduces hydrogen to ≤0.06 ml/100g for porosity-free material.
Step 3
DC Casting & Homogenisation
Cast into thick-section billets; 24+ h homogenisation soak at 460–480 °C dissolves Zn-Mg-Cu phases and reduces segregation.
Step 4
Hot Working
Rolled or forged at 380–440 °C through carefully controlled reduction ratios to develop the required wrought microstructure.
Step 5
Solution Treatment & Quench
Solution treatment at 465–475 °C followed by immediate cold-water or polymer quench — quench rate is critical to final strength.
Step 6
Multi-Stage Aging (T73/T76)
Two-step overaging (100 °C + 165 °C) provides resistance to stress corrosion cracking. Extensive tensile, fracture toughness, and SCC testing.
Chemical Composition
EN 573-3 / AA
Max % unless range shown. Balance: Al.
| Alloy | Chem. Symbol | Si | Fe | Cu | Mn | Mg | Cr | Zn | Ti |
|---|---|---|---|---|---|---|---|---|---|
| 7050 | AlZn6CuMgZr | 0.12 | 0.15 | 2.0–2.6 | 0.10 | 1.9–2.6 | 0.04 | 5.7–6.7 | 0.06 |
| 7068 | AlZn7.5MgCu | 0.12 | 0.15 | 1.6–2.4 | 0.10 | 2.2–3.0 | 0.05 | 7.2–8.2 | 0.10 |
| 7075 | AlZn5.5MgCu | 0.40 | 0.50 | 1.2–2.0 | 0.30 | 2.1–2.9 | 0.18–0.28 | 5.1–6.1 | 0.20 |