Materials
Heat Treatment Selector
See what condition and treatment we publish for a grade, and what each common treatment actually does - without inventing a temperature or a soak time.
As published
Aluminium 6061-T6
Treatments normally applied to this family
Stress relief
Heats the part below the transformation temperature, holds it, and cools slowly enough that no new stresses are added.
Why you would specify it: Removes the internal stresses left by machining, welding or forming. Specify it when the part will be machined in two stages and the second stage must not move the first, or when dimensions have to survive after the last cut.
Watch for: A stress-relieved part can still move when metal is removed afterwards: relief removes the stress that is there, not the imbalance the next cut creates.
Annealing
Heats to a defined temperature and cools slowly, softening the material and coarsening its structure.
Why you would specify it: Used to make a material machinable, or to remove the effects of prior working before a forming operation. On aluminium and copper alloys it is also used to restore ductility after bending.
Precipitation hardening (aging)
Holds the material at an elevated temperature so that fine particles precipitate out of solution and lock the structure.
Why you would specify it: How the 17-4 PH stainless and the nickel superalloys reach their strength. The part is normally machined in the softer solution-treated condition and hardens in place, which is easier to machine and, on complex parts, much easier to hold to size.
Watch for: Aging shrinks the part slightly and predictably. On a tight-tolerance feature, whether to machine before or after aging is a decision to take with the shop rather than from a table.
Solution treatment
Dissolves the alloying elements into a single structure at high temperature, then cools rapidly to hold them there.
Why you would specify it: The first half of the precipitation-hardening route, and the treatment that restores a superalloy or a PH stainless to a machinable, uniform condition after welding or forming.
Before you specify a treatment
- The material centre publishes Aluminium 6061-T6 as supplied in the condition "T6 - solution heat treated and artificially aged at the mill", with "There is no heat treatment after machining. The mill supplies T6 and nothing you do on a machine will raise it; welding drops the heat-affected zone back to O condition and it cannot be recovered without a full re-solution and age, which distorts the part." given as its heat treatment. That is the route we would quote from - the list below is what the treatment does, not a schedule.
- Heat treatment is a controlled special process: it is specified by a standard and comes with a certificate and a paper trail. Nothing on this page sets a temperature, a soak time or a hardness - those come from the specification the part is being made to.
- This is a precipitation-hardening material. Machining it in the soft condition and aging it afterwards is usually easier and cheaper than machining it hard, but the aging step moves the dimensions slightly - worth agreeing with the shop before the drawing is frozen.
Every treatment in the reference
- Stress relief11 families
- Annealing7 families
- Normalising3 families
- Through hardening (quench and temper)3 families
- Case hardening (carburising)1 families
- Nitriding4 families
- Induction hardening2 families
- Precipitation hardening (aging)6 families
- Solution treatment6 families
- Cryogenic treatment3 families
The condition and treatment shown are read from the published record for the grade you select. The descriptions are what each treatment does, not a schedule - temperatures, soak times and hardness come from the specification the part is made to.
What you provide
- Material grade
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