Common problems with 7075-T6 Aluminium and how to avoid them
7075-T6 Aluminium is a high strength aluminium alloy with zinc as the main addition, in the T6 temper. It is used for aerospace and motorsport parts where strength to weight is the deciding factor. This entry explains what it is, what the numbers on a data sheet mean, and what to put on a drawing.
It is written from the point of view of the buyer and the drawing office: the values that are realistic in production, the ones that cost money, and the way the result is verified. Where an industry sets the requirement, oil and gas is used as the example: materials that work harden and still have to be certified.
The problems that actually occur
These are the failures that show up on a real job, listed in the order in which they are usually discovered.
- Using it where 6082 would do, which adds cost for no gain. The cause is usually upstream: a datum that is not the functional one, a fixture that does not repeat, or a specification that cannot be measured the way it is written.
- Leaving it bare in a corrosive environment, because it pits. The cause is usually upstream: a datum that is not the functional one, a fixture that does not repeat, or a specification that cannot be measured the way it is written.
What causes them
In most cases the cause is upstream of the operation, not in it. Using it where 6082 would do, which adds cost for no gain is usually a symptom of one of the three causes above rather than a problem in its own right.
How they are prevented
Prevention is duller than diagnosis. Specify the temper and the cladding requirement, and the result is confirmed by standard dimensional inspection with a certificate check before the batch is released.
| Item | Note |
|---|---|
| Failure | using it where 6082 would do, which adds cost for no gain |
| Prevention | specify the temper and the cladding requirement |
| Tolerance to hold | ±0.01 mm |
| Finish to check | Ra 1.6 µm as machined |
Applications
7075-T6 Aluminium is used for aerospace and motorsport parts where strength to weight is the deciding factor, and in practice it appears most often in aerospace fittings, bicycle and motorsport components, mould plates, structural brackets.
How it fits into a machining route
7075-T6 Aluminium is chosen at the drawing stage, and everything downstream follows from it: the tool geometry, the cutting data, the heat treatment and the certificate. Changing the grade later is a different part, not a different quote.The route is fixed before the first part is cut, and it is the route rather than the individual setting that holds the result: material cost is several times that of 6061. Where a drawing calls for something the route cannot hold economically, that is raised at quotation rather than after the parts are made.
Standards, documentation and what is issued
The documentation requirement is AS9100 with material traceability. Material is supplied against a certificate where the application calls for it, inspection results are recorded with the job, and the records are kept so that a repeat order can be compared with the first instead of being measured from scratch.
Standard dimensional inspection with a certificate check is the verification step. Where a customer format or a standard report is required, it is agreed before the batch starts, because a report written after the event is a report nobody can use.
Frequently asked questions
What tolerance should be specified for 7075-T6 Aluminium?
±0.01 mm is realistic in production. Tightening it beyond the functional requirement increases cost without improving the part.
Which material is usually used?
7075-T6 aluminium is the usual choice, supplied against AS9100 with material traceability.
How is the result verified?
Standard dimensional inspection with a certificate check, with the results recorded so a repeat order can be compared with the first.
What is the most common mistake?
Leaving it bare in a corrosive environment, because it pits.
How long does it take and what does it cost?
A realistic cycle is fast, but with more tool wear than 6061, and the cost driver is material cost is several times that of 6061.
Related capability
If you are specifying 7075-T6 Aluminium on a drawing and want a second opinion on the route, send the model and the quantity. The first response is a manufacturability review with the likely risk points and a quotation, so the decision can be made on facts rather than on a price alone.
Machining, inspection and documentation are handled in one place, which is why the dimensional report and the material certificate arrive with the parts rather than after them.
Related entries
These entries sit next to 7075-T6 Aluminium in the encyclopedia: Duplex 2205 Stainless Steel, 4140 Alloy Steel, Bearing Housings. Reading them together gives a fuller picture of how the process, the material and the measurement affect each other.
