Material selection
Aluminum 6061 vs 7075
Both are machined the same way on the same equipment, so this is not a process decision, it is a strength decision. 7075 carries roughly twice 6061's yield strength, but it gives up weldability and corrosion resistance to get there, and it costs more to buy and more to cut. The numbers below are the same published values used on each material's own page, set side by side.
| Aluminum 6061 | Aluminum 7075 | |
|---|---|---|
| Density | 2.70 g/cm³ | 2.81 g/cm³ |
| Tensile strength | 310 MPa (T6) | 572 MPa (T6) |
| Yield strength | 276 MPa (T6) | 503 MPa (T6) |
| Elongation | 12 % | 11 % |
| Hardness | 95 HB | 150 HB |
| Melting range | 582–652 °C | 477–635 °C |
| Relative cost | Low | Medium |
Published values for standard grades at 23 °C unless stated, taken from each material's own datasheet page. Confirm against the supplier datasheet for the grade you specify.
What Aluminum 6061 is
6061 is a magnesium-silicon aluminum alloy and the most widely machined aluminum in the world. In the T6 temper it has roughly the yield strength of mild steel at a third of the weight, and it cuts at high spindle speed without work hardening. It anodises cleanly to a uniform finish, welds without difficulty, and is stocked everywhere in plate, bar, and extrusion. When a drawing says "aluminum" and nothing else, this is what it gets made from.
What Aluminum 7075 is
7075 is a zinc-alloyed aluminum with roughly twice 6061's yield strength, putting it in the range of medium-carbon steel while staying light. It is the standard choice for highly loaded machined structure in aerospace, motorsport, and robotics. The cost is corrosion resistance and weldability: 7075 is susceptible to stress corrosion cracking, and it is effectively unweldable by conventional methods, so joints are fastened or bonded rather than welded. Bare 7075 also pits in humid or salt environments and normally needs an anodised finish where 6061 would not.
Aluminum 6061 against Aluminum 7075
| Aluminum 6061 | Aluminum 7075 | |
|---|---|---|
| Strength | 276 MPa yield in T6, enough for most structural brackets and housings | 503 MPa yield, close to double 6061's, for highly loaded parts that would otherwise need steel |
| Weight for the same strength | Needs more cross-section to match 7075's load capacity, so a 6061 part carrying the same load is usually heavier | Carries the same load in less material at only 4 % higher density, the reason it is specified where weight and strength both matter |
| Weldability | Welds by TIG or MIG; the heat-affected zone loses temper and needs post-weld heat treatment on structural joints | Effectively unweldable by conventional methods; joints are fastened or bonded, not welded |
| Corrosion resistance | Anodises cleanly and holds up reasonably well bare in mild environments | Susceptible to stress corrosion cracking and pits in humid or salt air; anodising is close to mandatory, not optional |
| Machinability | Cuts fast at high spindle speed without work hardening, the easier of the two on tooling | Machines well but harder on tooling than 6061, with a stringier chip; still far easier to cut than stainless or titanium |
| Relative cost | Low, and the faster of the two to machine | Medium material cost, plus a machining-time premium over 6061 |
Which one, for which part
- A lightly loaded part, most brackets, housings, and mounting plates, is 6061's case: 7075 is simply a more expensive 6061 unless the load actually justifies the extra strength.
- A highly loaded structural part that would otherwise need to be steel, robotics arms and joints, motorsport uprights, aerospace fittings, favours 7075: roughly double the yield strength at only 4 % more density.
- A welded assembly, or a part joined by welding after machining, needs 6061; 7075 is not designed to be welded and stress corrosion cracking risk rises sharply near a weld-affected zone.
- A part exposed to salt spray or humid outdoor service without a coating step favours 6061; 7075 needs anodising close to mandatory to avoid pitting and stress corrosion.
- Jigs, fixtures, and tooling plates made on a machining budget favour 6061: it cuts faster, costs less, and rarely needs 7075's strength margin.
Our status
Trumould machines both aluminum 6061 and 7075 in-house on CNC; 6061 is also available through sheet metal fabrication, 7075 is not offered in sheet or through injection molding or 3D printing here. Send the part, its load case, and whether any joint will be welded, and the quote states which of the two is recommended and why, not just a price for whichever one you asked about first.
Specifying this part?
Send your CAD and target volumes. We come back with a price, a lead time, and any material or design notes that would reduce either.