MetalsWhat heat treatments exist for aluminum, copper, bronze and brass?
Not all metals harden the same way. Some gain hardness through heat treatment and others only through cold working. In this guide we explain what heat treatment means for aluminum, copper, bronze and brass, which ones can be treated and which cannot, and which process applies to each.
What is a heat treatment?
A heat treatment consists of heating the metal to a given temperature and cooling it in a controlled way to change its properties, mainly its hardness and strength. In these metals the process works differently than in steel, which is why it pays to understand how each one hardens.
Two ways to harden these metals
Aluminum, copper, bronze and brass gain hardness in two ways, and not all metals allow both:
- Cold working: when metal is bent, rolled or drawn cold, it hardens naturally. This is how 3003 aluminum, electrolytic copper and brasses are hardened. In their names it is identified by the letter "H" (for example, H14 or H04).
- Heat treatment: some metals are hardened by heating and cooling them in a controlled way. This is the case for 6061 and 7075 aluminum, beryllium copper and chromium coppers. In aluminum it is identified by the letter "T" (for example, T6 or T651).
The letters that accompany the name indicate how the metal was hardened. In aluminum: O is annealed (soft), H is cold-hardened (for example, H14) and T is heat treated (for example, T6 or T651). In copper: H is cold-hardened (H02, H04), and the aging tempers correspond to beryllium copper that has already been hardened.
Which metals are heat treated and which are not?
Not all metals can be heat treated. This table summarizes how each one we carry hardens:
| Metal | How does it harden? | Heat-treatable? |
|---|---|---|
| 3003 Aluminum | Cold work | No |
| 6061 and 7075 aluminum | Heat treatment (solution and aging) | Yes |
| C11000 copper (electrolytic) | Cold work | No |
| C17200 and C17510 beryllium copper | Heat treatment (precipitation) | Yes |
| C18000, C18150 and C18200 chromium coppers | Heat treatment (precipitation) | Yes |
| SAE 68 Aluminum Bronze | Heat treatment (quenching and tempering) | Yes |
| SAE 40, 62, 64 and 660 bronzes | Used as castings; properties depend on composition | No |
| C26000 and C36000 brass | Cold work | No |
The most commonly used heat treatments
These are the heat treatments most frequently applied to these metals:
Annealing. It consists of heating the metal and cooling it slowly to soften it. It is used to make the material easy to form, bend or machine, and it is applied to aluminum, copper and brass when they need to regain softness after being cold worked.
Precipitation hardening (solution treatment and aging). This is how 6061 and 7075 aluminum and beryllium copper harden. The metal is heated, cooled rapidly and then held at temperature for a time so that tiny particles form inside it and harden it. This final stage is called aging, and it is what gives the material its final strength.
Quenching and tempering. Aluminum bronze (SAE 68) is one of the few in this group that responds to a quench and temper similar to steel's, gaining mechanical strength and hardness. That is why it is used in gears and heavily loaded parts.
We deliver several grades already treated at the mill, so you skip that step. 6061 and 7075 aluminum come in T651 temper, beryllium copper comes hardened and chromium coppers come treated. In those cases you only need to machine the part.
Where are heat treatments done?
Heat treatments are performed by a specialized shop, with temperature-controlled furnaces. We do not perform the treatment, but we do supply the metal in the right grade and temper for your job, and in many cases it already comes treated from the factory. If you don't know which temper to order, we will advise you.
In summary
- A heat treatment changes the hardness and strength of the metal by heating and cooling it in a controlled way
- These metals harden by cold working (H tempers) or by heat treatment (T tempers)
- 6061 and 7075 aluminum, beryllium copper, chromium coppers and aluminum bronze are heat treated
- 3003 aluminum, pure copper, general-purpose bronzes and brasses are not heat treated
Why buy your metals at NAT MAC?
We have supplied metals to industry for more than 54 years and operate with ISO 9001 certified quality. We advise you on selecting the right metal, grade and temper for your part, and many grades already come heat treated from the mill.
- Aluminum, copper, bronze and brass in various grades and tempers
- Factory-treated grades, ready to machine
- Advice on choosing the right metal and temper for your part
- Cut to size
- Backed by ISO 9001 certified quality
Tell us what part you are going to make and how it will work, and we will help you choose the right metal and temper. Request your free quote.
Sources: NAT MAC Metals data sheets and catalog; ASM Handbook Vol. 2, Alloy and Temper Designation Systems for Aluminum; The Aluminum Association, International Alloy Designations and Chemical Composition Limits (Teal Sheets); Copper Development Association, alloy database (alloys.copper.org).
