Aluminum Alloy Grades and Temper Designations: A Complete Guide

If you work with aluminum products — whether you are a manufacturer, an engineer, or a buyer sourcing materials — you have probably seen designations like 5083-H116, 6061-T6, or 7075-O. These codes look complicated, but once you understand the system, reading them becomes second nature.

This guide breaks down aluminum alloy grade naming and temper designation in plain language. By the end, you will know exactly what each part of an aluminum designation means and how to choose the right material for your project.

1. What Is an Aluminum Alloy?

Pure aluminum is soft and not strong enough for structural use. An aluminum alloy is created by mixing pure aluminum with other elements — such as copper, magnesium, silicon, zinc, or manganese — to improve its strength, corrosion resistance, or workability.

Aluminum alloys are popular across industries because they offer:

• Light weight: About 1/3 the density of steel (2.7 g/cm³)
• High specific strength: Some alloys rival steel in strength-to-weight ratio
• Excellent corrosion resistance: Natural oxide layer protects the surface
• Good formability: Can be extruded, rolled, forged, and stamped
• Thermal and electrical conductivity: Second only to copper among common metals

If you are looking for aluminum alloy plates for marine, construction, or industrial applications, contact us to discuss your requirements.

2. How Aluminum Grade Naming Works

A complete aluminum designation has two parts:

1. The alloy grade (e.g., 5083, 6061, 7075) — tells you the chemical composition
2. The temper designation (e.g., -H116, -T6, -O) — tells you how the material was processed

For example, 5083-H116 means:

• 5083 = A 5xxx-series aluminum-magnesium alloy
• -H116 = Strain hardened with special corrosion resistance treatment

The naming system follows international standards (AA/Aluminum Association system), which is also adopted by most countries including China (GB/T), Europe (EN), and Japan (JIS).

3. The 8 Wrought Aluminum Alloy Series (1xxx–8xxx)

Wrought aluminum alloys (those that are mechanically worked by rolling, extrusion, or forging) are grouped into 8 series based on their primary alloying element. The first digit of the 4-digit grade tells you which series it belongs to.

Quick tip: For marine and shipbuilding applications, the 5xxx series (especially 5083 and 5086) and 6xxx series (especially 6082) are the most commonly used aluminum alloy plates. Learn more in our marine aluminum forming guide.

4. Understanding Temper Designations (F, O, H, W, T)

The temper tells you what processing the aluminum alloy has undergone after its initial production. This directly affects its strength, hardness, and formability.

There are 5 basic temper designations, each represented by a single letter:

5. H Temper in Detail: Strain Hardening Explained

The H temper is the most complex because it uses 2 or 3 digits after the letter H to describe the exact processing. Here is how to read it:

5.1 The First Digit After H — Type of Processing

5.2 The Second Digit After H — Degree of Hardening

5.3 The Third Digit After H — Special Variations

The third digit indicates a variation of the two-digit temper. Some common examples:

• H111: Slight strain hardening after annealing (less than H11). Common in extruded profiles that are straightened after annealing.
• H112: Products that acquire some temper through high-temperature forming processes. No special control over strain hardening, but mechanical property limits apply.
• H116: Special corrosion-resistant temper for 5xxx alloys with ≥4.0% magnesium. Provides excellent resistance to intergranular corrosion and exfoliation. This is the standard marine grade temper for 5083.
• H321: Similar to H116 but applies to alloys with lower magnesium content.

If you need 5083-H116 aluminum plates for marine construction, we stock this grade specifically for shipbuilding projects.

6. T Temper in Detail: Heat Treatment Explained

T temper applies to heat-treatable alloys (2xxx, 6xxx, 7xxx series). After the letter T, one or more digits describe the specific heat treatment sequence.

6.1 Common T Temper Codes

6.2 Understanding T6 — The Most Common Temper

T6 is the most widely specified temper for 6xxx-series alloys. The process involves:

1. Solution heat treatment: Heat the alloy to approximately 530°C to dissolve alloying elements into a solid solution.
2. Quenching: Rapid cooling (usually in water) to lock the elements in solution.
3. Artificial aging: Reheat to around 160–200°C for several hours to precipitate strengthening particles in a controlled way.

The result is a material with high strength and good ductility. For example, 6082-T6 aluminum plates are widely used in marine structures, bridges, and transport applications.

7. How to Read a Complete Aluminum Designation

Now that you understand both parts, here is how to read a full aluminum alloy designation like 5083-H116:

1. 5083: 5xxx series → aluminum-magnesium alloy → excellent marine corrosion resistance
2. H: Strain hardened (not heat treated)
3. 1: Only strain hardening was applied (no subsequent thermal treatment)
4. 16: Special variation for marine-grade corrosion resistance (exfoliation resistant)

Another example — 6061-T651:

1. 6061: 6xxx series → aluminum-magnesium-silicon alloy → heat treatable, good all-round properties
2. T6: Solution heat treated + artificially aged
3. 51: Stress relieved by stretching (1–3% permanent set)

8. Common Marine Aluminum Alloy Designations

If you are sourcing aluminum plates for shipbuilding or marine equipment, these are the grade designations you will encounter most often:

For more details about how these alloys are formed into ship components, read our guide on marine aluminum sheet forming technology.

9. Frequently Asked Questions

What does the “H” in 5083-H116 mean?

The “H” means the alloy has been strain hardened — strengthened by cold working (rolling or stretching) at room temperature. This is the standard way to increase strength in non-heat-treatable 5xxx-series alloys. The “116” suffix means it has special corrosion resistance treatment suitable for marine environments.

What is the difference between T4 and T6 temper?

Both undergo solution heat treatment, but T4 is naturally aged (left at room temperature) while T6 is artificially aged (heated in a furnace). T6 achieves higher strength because the controlled heating creates a finer, more uniform distribution of strengthening particles. However, T4 offers better formability immediately after quenching.

Why is 5083-H116 the standard for marine use?

5083-H116 combines the excellent seawater corrosion resistance of the 5xxx series with a special processing treatment that prevents intergranular corrosion and exfoliation. The H116 temper was specifically developed for marine applications where the material faces constant saltwater exposure. No other temper designation provides the same level of guaranteed corrosion resistance.

Can I weld 6061-T6 aluminum?

Yes, 6061-T6 can be welded, but you should know that the heat from welding will reduce the strength in the heat-affected zone (HAZ). After welding, the HAZ strength drops to roughly the T4 level. For critical structures, post-weld heat treatment may be required to restore the T6 properties. If weld strength retention is critical, consider 5083-H116 instead.

What does “O” temper mean and when should I use it?

O temper (annealed) is the softest, most ductile condition. Use it when you need to deep draw, bend, or form the aluminum into complex shapes that would crack in harder tempers. After forming, the part can sometimes be heat treated (for heat-treatable alloys) to increase its final strength.

How do I know if an alloy is heat treatable?

Check the series number: 2xxx, 6xxx, and 7xxx series are heat treatable. 1xxx, 3xxx, 4xxx, and 5xxx series are NOT heat treatable — they can only be strengthened by strain hardening (cold working). This is why 5xxx marine alloys always use H tempers, while 6xxx structural alloys use T tempers.

Is the aluminum alloy naming system the same worldwide?

The Aluminum Association (AA) system used in the United States is the most widely adopted standard globally. European (EN), Japanese (JIS), and Chinese (GB/T) systems have minor differences. For example, 5083 in AA is equivalent to EN AW-5083 and GB/T 5083. However, slight differences in allowed composition ranges may exist between standards, so always verify the specific standard when ordering.

10. Conclusion

Understanding aluminum alloy grade designations and temper codes is essential for selecting the right material for your project. Here is a quick summary:

• The 4-digit grade tells you the chemical composition (5083 = Al-Mg, 6061 = Al-Mg-Si, etc.)
• The temper letter tells you the processing method (F = as-fabricated, O = annealed, H = strain hardened, T = heat treated)
• The digits after the temper letter specify the exact processing details and resulting properties
• For marine applications, 5083-H116 is the gold standard for corrosion resistance
• For structural applications requiring heat treatment, 6061-T6 and 6082-T6 are the most versatile choices

Need aluminum alloy plates for your project? We stock a full range of marine-grade and industrial aluminum alloy sheets, including 5083-H116, 6082-T6, 6061-T6, 5052-H32, and more. Contact our team or reach us on WhatsApp: +86 13305709557 for a quote and technical consultation.