Choosing an aluminium grade: 6061, 6063, 7075 and the tempers that matter
July 24, 2026
Aluminium covers most of what gets machined and shipped internationally. Picking the grade well affects price, lead time, finish quality and how much the part moves after machining. Picking it badly usually shows up as a surprise in one of those four.
The three you will meet most
6061, the default. Medium strength, excellent machinability, good corrosion resistance, welds and anodises well. Available everywhere as plate, bar and extrusion. If nothing in your design argues otherwise, this is the grade.
6063, the extrusion grade. Lower strength than 6061 but a better surface finish and a cleaner anodised appearance. Common as extruded profile. It is a good choice for visible parts and enclosures, and a poor choice where the part carries load.
7075, the strong one. Aerospace grade, roughly double the yield strength of 6061. Machines well but is more expensive, less corrosion resistant, harder to weld and less predictable to anodise. Use it where strength to weight genuinely drives the design.
| Grade | Yield strength, typical | Machinability | Anodising | Notes |
|---|---|---|---|---|
| 6061-T6 | 275 MPa | Excellent | Excellent | The default for most parts |
| 6063-T5 | 145 MPa | Good | Excellent | Extrusions, visible surfaces |
| 7075-T6 | 500 MPa | Good | Fair | Strength critical, coated |
| 2024-T3 | 325 MPa | Good | Poor | Aerospace legacy, corrodes |
| 5083 | 215 MPa | Fair, gummy | Fair | Marine, welded structures |
Figures are typical published values for planning, not certified properties for your lot.
Temper matters more than buyers expect
The letter and number after the grade describe the heat treatment and, sometimes, a stress relief.
- T6 is solution treated and artificially aged, the common strong condition
- T651 adds stress relief by stretching. On thick plate this is what keeps a large flat part flat after material is removed
- T5 is cooled from extrusion and aged, typical for 6063 profiles
- O is annealed, soft and easy to form, rarely what you want for a machined part
If your part is a large plate with a lot of material removed from one side, asking for T651 and discussing stress relief is worth doing. Parts that bow after machining are almost always a stress problem, not a machining problem.
What machines well and what does not
Aluminium is generally forgiving. The differences that matter in practice:
- 6061 and 7075 chip cleanly at high speed and give a good finish
- 5083 and other 5000 series are gummy and tend to smear, which shows on finished surfaces
- Cast aluminium can contain hard spots and porosity, which is fine for rough parts and a problem for sealing faces
On thin walls, aluminium’s low stiffness is the limit rather than its hardness.
Availability, which drives lead time
In Vietnam, 6061 and 6063 in plate, bar and common extrusions are stocked locally. That means days, not weeks. 7075 is available but more often ordered in, and a specific heat with a mill certificate is an import item.
This is why a material line in a request should say two things: the grade you want, and whether an equivalent local grade is acceptable. That single sentence can move a quote by two weeks.
Finish and appearance
If the part is visible, say so, and say whether colour consistency matters across a batch. Anodised colour varies with alloy, with surface preparation and with bath conditions. Mixing 6061 and 6063 parts in one assembly and anodising them together will usually show a visible difference.
For cosmetic parts, approve a first sample for colour and keep it as the reference.
What to put in your request
Material: aluminium 6061-T651 plate. Local equivalent acceptable. No mill certificate required. Parts are visible in the assembly, anodised black Type II, colour to match approved sample.
Reading a supplier’s aluminium offer
When a quote comes back, three lines tell you whether the shop has thought about material at all.
The form it will buy. Plate, bar, extrusion or a sawn billet. A part cut from 60 mm plate when 50 mm would have done is paying for 10 mm of chips on every piece. Ask which stock size the quote assumes, and whether a small design change would land on a standard thickness.
Whether the price includes saw cutting and facing. Stock arrives oversize. Someone pays for getting it square. On small orders this is a visible part of the price and it is often where two quotes differ.
What happens to offcuts. On expensive grades, ask whether offcuts are credited or kept. It rarely changes a small order and it matters on 7075 at volume.
Common mistakes worth avoiding
- Specifying 7075 because it sounds better. It is harder to anodise consistently, corrodes faster and costs more. If the part is a mounting bracket, 6061 is the engineering answer.
- Mixing grades in a visible assembly. Two anodised parts in different alloys will not match, and the customer will notice before you do.
- Ignoring stress on large plates. A 300 mm plate with deep pockets on one side will bow. Ask for T651 stock and, on critical parts, a rough machine, stress relieve and finish sequence.
- Leaving the temper off the drawing. “6061” alone allows annealed stock, which is half the strength you assumed.
That is enough for any shop to buy stock and quote without a round of questions. The related guides on material substitution and on surface finishing cover the two decisions that usually follow. When you are ready, send the drawing.
Questions we get on this
Is 7075 worth the price over 6061?
Only when you need the strength. 7075-T6 is roughly twice as strong as 6061-T6 in yield, costs considerably more per kilogram, welds poorly and corrodes more readily unless coated. For most brackets and housings 6061 is the better engineering answer.
Which aluminium anodises best?
6061 and 6063 both anodise well and take dye consistently. 7075 anodises but tends toward a darker, less predictable colour, and high copper alloys such as 2024 are difficult to anodise cleanly.
What does the T6 mean?
It is the temper, meaning solution heat treated then artificially aged. T6 is the common strong condition. T651 adds a stress relief by stretching, which matters on plate because it reduces movement after machining.
Have a part like this?
Send the drawing. We shortlist the shop we place it with that run the process and material, and answer within 24 business hours.
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