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Dr. Dmitri Kopeliovich
According to the Wrought aluminum alloys designation system, alloys of this series are designated 7xxx.
This group includes zinc (Zn) and magnesium (Mg) as the major alloying elements.
Copper (Cu), manganese (Mn), chromium (Cr) and zirconium (Zr) may be added to the alloys of 7xxx series as minor alloying elements.
Aluminum-zinc-magnesium alloys are heat-treatable.
Solution treatment followed by either artificial or natural aging allows considerable increasing the yield strength (3-5 times). Ductility of the alloy decreases as a result of the heat treatment.
Hardening of the alloys from this group is achieved due to precipitation of the phases MgZn2 and Mg3Zn3Al2t occurring during aging.
Alloys of this series possess the highest mechanical strength when heat treated. corrosion resistance of aluminum-zinc-magnesium alloys is good particularly in the alloys containing small amount of copper. Weldability and formability of the alloys are quite good if the total amount of the alloying elements is below 8%.
Small amounts of zirconium, chromium and manganese may be added for obtaining fine grain structure and inhibiting recrystallization during solution treatment.
Aluminum-zinc-magnesium alloys (7xxx series) are used in various aircraft structures (forgings, extrusions, sheets) and for manufacturing hydraulic equipment.
| Designation | Cu,% | Mn,% | Mg,% | Cr,% | Zn,% | Zr,% |
|---|---|---|---|---|---|---|
| 7001 | 1.6-2.6 | 0.2 max. | 2.6-3.4 | 0.18-0.35 | 6.8-8.0 | - |
| 7005 | 0.10 max. | 0.2-0.7 | b 1.0-1.8 | 0.06-0.20 | 4.0-5.0 | 0.08-0.20 |
| 7008 | 0.05 max. | 0.05 max. | 0.7-1.4 | 0.12-0.25 | 4.5-5.5 | - |
| 7039 | 0.10 max. | 0.1-0.4 | 2.3-3.3 | 0.15-0.25 | 3.5-4.5 | - |
| 7049 | 1.2-1.9 | 0.20 max. | 2.0-2.9 | 0.10-0.22 | 7.2-8.2 | - |
| 7050 | 2.0-2.6 | 0.10 max. | 1.9-2.6 | 0.04 max. | 5.7-6.7 | 0.08-0.15 |
| 7072 | 0.10 max. | 0.10 max. | 0.10 max. | - | 0.8-1.3 | - |
| 7075 | 1.2-2.0 | 0.30 max. | 2.1-2.9 | 0.18-0.28 | 5.1-6.1 | - |
| 7108 | 0.05 max. | 0.05 max. | 0.7-1.4 | - | 4.5-5.5 | 0.12-0.25 |
| 7178 | 1.6-2.4 | 0.30 max. | 2.4-3.1 | 0.18-0.28 | 6.7-7.3 | - |
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