Material Group 23.2 ISO/TR 15608:
Heat treatable aluminium-zinc-magnesium alloys.
7000 series are alloyed with zinc, and can be precipitation hardened to the highest strengths of any aluminium alloys. Most 7000 series alloys include magnesium and copper as well.
Features of EN AW-7020 alloy
EN AW-7020 is a typical alloy (Cu-free) in this Al-Zc-Mg alloy material group. Generally Al-Zc alloys are precipitation-hardened aluminium alloys. They are commonly available in pre-tempered grades such as 7020-T6 with specified yield strength Rp0,2 > 290 MPa (T6).
The most common temper heat treatment (description in EN 515) for 7020 aluminium is:
T4: Naturally aged to a stable condition
T6: Solution heat treated, quenched and artificially aged
EN AW-7020 material is weldable by standard techniques. The alloy exhibits a good recovery of mechanical properties after welding, approaching the original values of the base metal (depending on welding conditions). These properties can be achieved after natural aging for a prolonged period or after an additional artificial aging treatment.
In Al-Zn-Mg alloys(Cu-free) , strength in the heat effect zone (HAZ) is reduce due to the re-solution of the precipitates. In this case, natural or preferred weldable EN AW-7020 offers unique possibilities due to
- large solid solution range from 350-500°C
- low quench rate sensitivity
- significant age-hardening effect at room temperature
The HAZ reaches the original strength after 90 days of natural ageing.
Note: EN AW-7075 materials with copper can only be welded to a limited extent or not at all (risk of hot cracking).
Applications of EN AW-7020 alloy
Typical applications are highly loaded construction parts and hydraulic applications in acc. to EN 1392 “Aluminum and aluminum alloys – Wrought and cast products – Particular requirements for products for the fabrication of pressure equipment” see table below.
According to EN 602, the use of the EN AW-7020 material is NOT allowed the contact with food.
Table: Weldability and pressurised applications for aluminium alloy material group 23.2 in acc. to EN 1392:
| Material | Condition 1 | Weldability | Application | min./max. Working Temp. |
|---|---|---|---|---|
| EN AW-7075 | T73 | No | only hydraulic applications | -273/160 °C |
Typical materials in group 23.2
| Name | Number | Standard | Product | Remark |
|---|---|---|---|---|
| EN AW-AlZn4,5Mg1,5Mn | EN AW-7005 EN AW-7005 EN AW-7005 | EN 485-2 EN 754-2 EN 755-2 | Plate Cold drawn rod/bar and tube Extruded rod/bar, tube | EN 13445-8: No EN 13445-8: No EN 13445-8: No |
| EN AW-AlZn4,5Mg1 | EN AW-7020 EN AW-7020 EN AW-7020 | EN 485-2 EN 754-2 EN 755-2 | Plate Cold drawn rod/bar and tube Extruded rod/bar, tube | EN 13445-8: No EN 13445-8: No EN 13445-8: No |
| EN AW-AlZn5,5MgCu EN AW-AlZn5,5MgCu EN AW-AlZn5,5MgCu | EN AW-7075 EN AW-7075 EN AW-7075 | EN 485 EN 754 EN 755 | Plate, sheet, stripe Cold drawn rod/bar and tube Extruded rod/bar, tube | not weldable not weldable not weldable |