MATERIALS EXPLAINED
6061-T6: what heat treatment does to a forged part
Forging shapes the part; T6 heat treatment gives it strength. Here is what the two letters mean and why nearly every structural forged aluminum part carries them.
What ‘T6’ actually means
T6 = the metal is solution heat-treated (heated until alloying elements dissolve, then quenched fast) and artificially aged (held warm so hardening precipitates form throughout the metal).
The result on 6061: tensile strength jumps from roughly 170 MPa as-forged to 310 MPa in T6 — without adding a gram of weight. The same logic applies to 7075 (572 MPa in T6) and 6082.
Every XPF batch runs through controlled solution treatment and ageing, traceable by its mill certificate.
What it means when you buy
Predictable strength
T6 minimums (310 MPa tensile / 276 MPa yield for 6061) are guaranteed properties, not typicals.
Traceable batches
Mill certificates tie every shipment back to its heat-treatment lot.
Design freedom
Machining after T6 keeps precision features precise — one reason forged-then-machined beats welded assemblies.
Watch-outs
Post-T6 welding or overheating locally softens the part. Design for it — our DFM review flags it free of charge.
Temper quick reference
| Temper | Meaning | Typical use |
|---|---|---|
| F | As-forged, no treatment | Blank state before heat treatment |
| O | Annealed (soft) | Maximum formability |
| T4 | Solution + natural ageing | Formable, strengthens over time |
| T6 | Solution + artificial ageing | The structural default — max strength |
| T651 | T6 + stress-relieved by stretching | Machined plate stock |
Related reading: 6061 vs 7075 comparison · 6061 properties · 7075 properties.
FAQ
Common questions
What does T6 mean in 6061-T6?
T6 = solution heat-treated, then artificially aged. The two steps precipitate hardening phases inside the metal, roughly doubling strength over the as-forged state.
Why is T6 the standard for forged parts?
It delivers the best combination of strength and machinability for structural use — the industry default for forged bicycle, automotive and industrial components.
Does forging happen before or after T6?
Before. The part is hot-forged, then solution-treated and aged. Forging first aligns the grain; T6 then sets the final strength.
What temperatures are involved?
Solution treatment around 530 °C followed by rapid quench, then artificial ageing around 175 °C — precisely controlled per batch.
Does T6 affect corrosion resistance?
6061-T6 retains excellent corrosion resistance; that is part of why the alloy is so widely specified for outdoor and anodised parts.
Can T6 parts be re-welded or re-heated?
Welding or overheating locally dissolves the hardening precipitates and loses strength in that zone — design one-piece forgings instead of welded assemblies where loads are critical.
What is T651?
T651 is T6 plus a controlled stretching step after quench to relieve internal stress — common on plate stock used for machining.
Do you supply T6 certificates?
Heat treatment is batch-controlled; mill certificates and dimensional reports accompany every shipment, with PPAP/FAI on request.
Does anodising affect T6 strength?
Standard Type II anodising does not significantly affect temper. Type III (hard anodising) is also compatible when specified correctly.
How do I specify T6 on a drawing?
Note the alloy and temper (e.g. ‘6061-T6 per ASTM B221’) — we forge, heat-treat and certify to it.
MATERIAL GUIDES
6061 properties · 7075 properties · 6061 vs 7075 · What is billet aluminum · Forging vs casting · Forged blanks vs billet
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