Cracking the Code: Understanding Aluminum Tempers (T4, T6, H112) for Your Next Project

If you have ever shopped for metal materials in the USA, you know that buying an aluminum bar isn’t as simple as just picking a size. You are often met with a string of cryptic letters and numbers following the alloy grade, such as “6061-T6” or “5083-H112.”

For DIY enthusiasts, engineers, and fabricators alike, these codes—known as temper designations—are the difference between a project that succeeds and one that snaps under pressure. At Aluminium Tubes, we believe that knowing your materials is just as important as the design itself.

In this guide, we will get the aluminum temper designation explained in plain English, focusing on the three most common designations you’ll encounter: T4, T6, and H112.

The Basics: What is an Aluminum Temper?

While the alloy number (like 6061 or 3003) tells you what ingredients are in the metal (magnesium, silicon, copper, etc.), the temper tells you what the metal has been through to get to its current state.

Aluminum can be strengthened through heat treatment or strain hardening (cold working). The Aluminum Association uses a standard system to identify these treatments. The letter generally indicates the basic treatment class:

• F: As fabricated (no special control).
• O: Annealed (softest state).
• H: Strain-hardened (strengthened by cold working, like rolling).
• T: Thermally treated (heat-treated),.

Let’s dive into the specific tempers you are most likely to find on our shelves.

T6 Temper Definition: The Strength Standard

When you see “T6,” think “maximum strength.” This is the gold standard for structural applications.

The T6 temper definition refers to a process where the aluminum is solution heat-treated and then artificially aged. In practical terms, the metal is heated to a high temperature, cooled (quenched), and then held at a lower elevated temperature in a furnace for a specific time to lock in its mechanical properties.

Why choose T6?

• High Strength: 6061-T6, for example, has a yield strength of about 40,000 psi (276 MPa), making it ideal for heavy-duty load-bearing applications.
• Rigidity: It is excellent for structures that need to maintain their shape without bending.

However, this strength comes with a trade-off. T6 aluminum has lower ductility (around 8–10% elongation), meaning it is harder to bend without cracking compared to softer tempers.

Best Uses: Bicycle frames, automotive chassis, aerospace structures, and heavy-duty structural components.

T4 Temper: The Formable Alternative

If T6 is the strong, rigid sibling, T4 is the flexible one. The T4 designation means the metal was solution heat-treated and then naturally aged to a stable condition,. Instead of being baked in a furnace to age (like T6), it is allowed to age at room temperature.

Why choose T4?

• Workability: T4 offers excellent formability and ductility (10–16% elongation).
• Fabrication: It is the go-to choice if your project involves bending the aluminum bar or tube.

If you try to bend a T6 bar 90 degrees, it might snap. If you do the same with a T4 bar, it is much more likely to bend cleanly. Interestingly, some fabricators form the metal in the T4 state and then artificially age it to T6 afterward to get the best of both worlds.

H112 Aluminum Bar Uses: The Extruder’s Choice

The H112 designation is unique and often misunderstood. Unlike T-tempers, which rely on heat treatment, H-tempers are generally for non-heat-treatable alloys (like the 5000 series).

H112 applies to products that acquire some temper (hardening) just from the shaping process itself—usually extrusion or hot rolling—without special control over the amount of strain hardening,. However, unlike “As Fabricated” (F) materials, H112 products must still meet specific mechanical property limits.

H112 aluminum bar uses typically involve the 5000-series alloys, such as 5083. This temper is common in:

• Marine Applications: Because alloys like 5083-H112 offer exceptional corrosion resistance in saltwater.
• Fluid Handling: Extruded tubes and pipes used in hydraulic or pneumatic systems often utilize this temper.

If you are looking for a marine-grade aluminum bar that offers moderate strength and high corrosion resistance, you will likely be looking at an H112 specification.

How to Choose Aluminum Temper for Your Project

Knowing how to choose aluminum temper comes down to three main questions regarding your project’s needs:

1. Do you need to bend it? If you are building a custom roll cage or a curved architectural feature, choose T4. Its higher ductility allows for forming without failure.
2. Does it need to support heavy weight? If you are building a workbench, a trailer frame, or a support beam, choose T6. The heat treatment provides the yield strength necessary to resist deformation under load.
3. Is it for a marine environment? If the project is on a boat or a dock, look for 5000-series alloys (like 5083 or 5086) in the H112 temper. These offer the best protection against the elements,.

Aesthetics and Finish: Black Aluminum Flat Bar

Once you have selected the right alloy and temper, you often have to consider the finish. At Aluminium Tubes, we see high demand for black aluminum flat bar.

Usually made from 6061-T6 or 6063-T5, these bars are often anodized. Anodizing is a surface treatment that thickens the natural oxide layer on the aluminum part. This not only creates a sleek, professional black finish but also increases corrosion resistance and surface hardness. Whether for architectural trim, custom furniture, or framing, a black anodized flat bar provides a “finished” look right off the shelf, saving you painting time.

Conclusion

Whether you are an engineer specifying materials for an aerospace application or a hobbyist building a custom rig in your garage, understanding the difference between T6 strength, T4 formability, and H112 utility is essential.

At Aluminium Tubes, we are dedicated to helping our US customers find the exact grade and temper they need. From high-strength structural tubes to versatile aluminum bar stock, we have the inventory and the expertise to get your project moving.

Need help selecting the right aluminum for your next build? Browse our catalog today or contact our support team for expert advice.