7075-T6 Aluminium vs Inconel 718: which one fits your part
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, semiconductor is used as the example: cleanliness and surface condition that matter more than the nominal size.
The short answer
7075-T6 Aluminium and Inconel 718 overlap, but they are not interchangeable. Choose 7075-T6 Aluminium when the requirement is aerospace and motorsport parts where strength to weight is the deciding factor; choose Inconel 718 when the requirement is turbine, downhole and high temperature parts where creep and oxidation set the limit.
Side by side
| Point of comparison | 7075-T6 Aluminium | Inconel 718 |
|---|---|---|
| What it is | a high strength aluminium alloy with zinc as the main addition, in the T6 temper | a nickel chromium super alloy that holds strength at high temperature |
| Used for | aerospace and motorsport parts where strength to weight is the deciding factor | turbine, downhole and high temperature parts where creep and oxidation set the limit |
| Typical tolerance | ±0.01 mm | ±0.02 mm |
| Surface finish | Ra 1.6 µm as machined | Ra 1.6 µm as machined |
| Cost driver | material cost is several times that of 6061 | tool consumption and cutting time |
Which one fits your part
Work from the feature that has to work. If the requirement is aerospace and motorsport parts where strength to weight is the deciding factor, 7075-T6 Aluminium is the safer call; if it is turbine, downhole and high temperature parts where creep and oxidation set the limit, Inconel 718 wins on cost or on lead time. Where the drawing does not make it clear, that is the question to settle before quotation rather than after.
A note on specification
Write the drawing so that either route can be considered where the function allows. That keeps the quotation competitive and stops a process being specified where a result should have been.
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: 316L Stainless Steel, 304 Stainless Steel, Splined Shafts. Reading them together gives a fuller picture of how the process, the material and the measurement affect each other.
