Classification and Grades of Aluminium

Aluminium has long become a material that modern industry cannot do without. It is used across dozens of sectors: from wires to architectural facades, from foil to aircraft parts, and each of them imposes specific requirements on strength, ductility, corrosion resistance, anodizing capability, or formability. In its pure form, aluminium is too soft, easily deforms, and loses its properties under load. That is why industry relies not on the pure metal, but on its alloys. The addition of alloying elements changes aluminum’s behavior and, accordingly, its field of application. To precisely match the material to the task, a classification and marking system is used.

How it works

Marking is not just a combination of letters and numbers. It is a code that encodes the composition, production method, and behavior of the alloy under real conditions. Understanding the marking system allows one to predict in advance how a material will behave during processing: whether it can be welded, whether it is suitable for anodizing, whether it will retain its shape during stamping, and how reliably it will perform under load. Navigating this system is not difficult. It is enough to understand the main groups and principles upon which the markings are based. In this article, we explain what aluminium grades exist, how their designation system is structured, and how to apply this knowledge in working with the material.

The classification system for aluminium is based on two principles: chemical composition and processing method. The first distinguishes pure aluminium from alloys containing various alloying additions. The second defines how the material was manufactured: cast into a mold or deformed under pressure (i.e. casting and wrought alloys, each with their own physical and mechanical properties and fields of application).

After the primary division into casting and wrought alloys, the classification continues within each group

Decoding Aluminium Alloy Designations

Aluminium alloy grades are represented by an alphanumeric code that encodes the alloy’s composition, processing characteristics, and physical-mechanical properties.

The first letter in the marking is “A”, indicating aluminium as the base metal. Subsequent letters designate the alloying elements, listed in descending order of their influence on the alloy’s properties. If there are several additions, a combined designation is used. Numbers following the letters indicate the approximate percentage of these elements. For example, АК5М2 is an aluminium alloy with 5% silicon and 2% magnesium. Thus, the marking instantly reveals the chemical base and helps predict how the alloy will behave during processing or in operation.

But the decoding does not end there. Additional symbols can be used in the marking to specify the condition of the material, the processing method, or the type of subsequent mechanical treatment:

·       T, T1–T7 — heat-treated conditions with various aging modes

·       M — soft (annealed)

·       H — strain-hardened (without thermal treatment)

·       H1–H3 — degrees of strain hardening

·       P — extruded

·       A, B, U — various types of cladding

It is important to note that the same letters may have different meanings depending on their position in the marking. For example, the letter “M” can indicate either the material’s condition or a modified alloy composition. In condition markings, it refers to a “soft” (annealed) alloy and usually appears after a hyphen, as in АМг6-М or АД31-М. In contrast, in the grade АМг6М, the same letter denotes a modified version of the base alloy with different composition or properties. Context helps distinguish between the two: if “M” follows a number without a hyphen, it signifies modification; if after a hyphen — material condition. These distinctions are crucial when selecting aluminium for specific manufacturing processes, especially welding, anodizing, or forming.

Numerical Classification of Wrought Aluminium Alloy

In addition to the alphanumeric system, a numerical designation scale is also used. It covers both technical-grade aluminium and complex alloys. Below is a general summary:

Standards in Ukraine

Ukraine applies a system of DSTU standards harmonized with European norms. These standards ensure a clear and accurate description of material properties, allowing aluminium alloys to be used in engineering and production documentation without discrepancies under uniform technical conditions, including for international projects and deliveries.

DSTU EN 573-1 is used for wrought alloys:

EN 573-1 Classification

DSTU EN 1706 is used for casting alloys:

EN 1706 Classification

High-purity aluminum is classified according to DSTU EN 573-3, which defines the composition and purity levels of wrought aluminum alloys. Depending on the content of the main element (Al), a distinction is made between: