The Ultimate Guide to Aluminum Naming Conventions

Have you ever seen a label like "Aluminum 6061-T6" and wondered what it meant? It might look like a random string of characters, but it’s actually a highly specific and universal language. The naming convention for aluminum alloys, standardized by organizations like The Aluminum Association, is a precise system that tells engineers, designers, and manufacturers everything they need to know about a material’s composition and history. Let’s break down this naming system into its core components.

1. The Two Halves of the Name

The first thing to understand is that a full aluminum alloy name is typically made of two parts, separated by a dash.

• Part 1: The Alloy Designation (e.g., 6061): A four-digit number that identifies the alloy’s chemical composition—its "ingredients."
• Part 2: The Temper Designation (e.g., -T6): An alphanumeric code that describes the mechanical or thermal treatment the alloy has received to achieve its final strength and hardness.

Together, these two parts give a complete picture of the material’s identity and properties.

2. The Four-Digit Alloy Designation: The Core Identity

The four-digit number is the alloy’s fundamental name. It specifies the primary alloying elements and the unique recipe. This system is primarily for wrought alloys (alloys that are mechanically worked into shape). The most important digit is the first one, which defines the alloy’s main "family."

• 1xxx Series: Commercially Pure Aluminum
• 2xxx Series: Alloyed with Copper (for high strength)
• 3xxx Series: Alloyed with Manganese (a general-purpose workhorse)
• 4xxx Series: Alloyed with Silicon (for welding and brazing)
• 5xxx Series: Alloyed with Magnesium (for excellent corrosion resistance)
• 6xxx Series: Alloyed with Magnesium and Silicon (a versatile, all-around performer)
• 7xxx Series: Alloyed with Zinc (for the absolute highest strength)
• 8xxx Series: A catch-all for other elements like Lithium.

3. The Temper Designation: Defining the Condition

The temper designation, following the dash, is just as critical as the alloy number. It describes the "condition" of the metal—whether it’s soft and formable or hardened for maximum strength. The main temper categories are indicated by a letter:

• -F (As Fabricated): This means the alloy has no special treatment after its initial manufacturing process. Its properties can be inconsistent.
• -O (Annealed): The alloy has been heated and slowly cooled to relieve internal stresses. This results in the softest, most ductile, and most workable state.
• -H (Strain-Hardened): The alloy has been strengthened through mechanical work (like rolling or stretching) at room temperature. Numbers follow the "H" (e.g., -H32, -H38) to indicate the degree of hardening and any subsequent treatments. This is only applicable to non-heat-treatable alloys (like the 3xxx and 5xxx series).
• -T (Thermally Treated): The alloy has been strengthened through heat treatment, often involving a sequence of heating and cooling (quenching) followed by aging. A number following the "T" (e.g., -T4, -T6) specifies the exact sequence of treatments. This is used for heat-treatable alloys (like the 2xxx, 6xxx, and 7xxx series).

4. Putting It All Together: A Naming Example

Let’s decode a common alloy used in marine applications: 5052-H32.

• 5052:
  • The 5 tells us it’s in the 5xxx series, so its primary alloying element is Magnesium. We can immediately infer it has excellent corrosion resistance.
  • The 0 indicates it’s the original formulation in its group.
  • The 52 is the specific identifier for this alloy within the series.
• -H32:
  • The -H tells us it is strain-hardened, not heat-treated.
  • The 32 is a more complex code. The "3" means it has been strain-hardened and then stabilized at a low temperature. The "2" indicates the final degree of hardness, which is 1/4 hard (harder than annealed, but still quite formable).

From the name 5052-H32, an engineer knows they have a moderately strong, highly corrosion-resistant, and stable aluminum alloy.

5. A Note on Cast Alloys: The Other Naming System

It’s important to know that there is a separate naming system for cast alloys—alloys designed to be melted and poured into a mold. These names look slightly different, often following a xxx.x format (e.g., A356.0).

• The first digit still represents the main alloy group (e.g., 3xx.x is a Silicon + Copper/Magnesium alloy).
• The next two digits are the specific alloy identifier.
• The number after the decimal point indicates if it’s a final casting (.0) or an ingot (.1 or .2).
• A letter prefix (like A in A356.0) indicates a modification to the original alloy.

While the details differ, the principle remains the same: a standardized name that precisely communicates the material’s identity.