Aluminum Tempers Explained: Designation, Properties, Uses, and Manufacturing Process

If you are a purchaser or a part manufacturer, you likely know that aluminum alloy stock is not always the same—even for the same aluminum alloy with the identical chemical composition.

To take advantage of aluminum’s low density for lightweight applications, you choose specific variations:

• Architectural & Decoration: You might use 6063-T5 aluminum for window frames and other extrusions.
  
• Automotive & Cycling: You likely require 6061-T6 aluminum for chassis brackets, pedals, and other structural parts made via precision CNC machining.
  
• High-Volume Hardware: You might opt for 5052-H32 aluminum for fasteners, bolts, and nuts produced through stamping, or just for sheet metal fabrication.

These variations are not random. How do tempers like "T" and "H" fit into the aluminum alloy designation system? What do the suffix numbers represent? How do they affect machinability and determine material properties? This article provides the most comprehensive guide to aluminum temper designations, their effects on manufacturing, and the most popular applications for tempered aluminum.

Aluminum Tempers: A Quick Overview

As a core part of the aluminum alloy designation system, the temper significantly impacts the mechanical properties of aluminum alloys, which in turn dictates how they are processed and used——

The temper suffix determines the success or failure of a part. It directly alters the material's hardness, tensile strength, and stability, influencing its performance during CNC machining, sheet metal fabrication, and other manufacturing processes.

We categorize aluminum tempers into several basic groups, with a primary focus on H tempers and T tempers:

1. Basic Tempers

2. H Tempers: Strain-Hardened (Non-Heat-Treatable Alloys)

Applicable to the 3xxx and 5xxx series non-heat-treatable aluminum alloys. Strength is basically increased through cold working such as cold rolling or cold bending. 

Note: You can refer to the Aluminum Association standards to distinguish between heat-treatable and non-heat-treatable aluminum alloys.

3. T Tempers: Thermally Treated (Heat-Treatable Alloys)

Applicable to the 2xxx, 6xxx, and 7xxx series of heat-treatable aluminum.

Examples: Popular Aluminum Alloys and Tempers

In your lightweight projects, selecting the right alloy and the correct aluminum temper determines if the part can survive its operating environment. Here are the most searched combinations by global buyers and engineers:

Conclusion

Understanding aluminum tempers is not only for select the right aluminum, it is also essential for optimizing production costs and ensuring part quality. For non-heat-treatable series (3xxx/5xxx), the H temper determines formability. For heat-treatable series (6xxx/7xxx), the T temper (especially T6, T651, and T73) is about the trade-off between "maximum strength" and "optimum dimensional stability" for the aluminum CNC machining.

If you are unsure which state to choose during product development or have questions about the manufacturing effects on aluminum parts, Contact VMT CNC Machining Factory for more of aluminum CNC machining parts. Our engineering team will provide the most professional advice based on your application (aerospace, automotive, electronics), manufacturing needs (bending, welding, or precision cutting), and budget.

Case Study: Why We Machined 6061-T651 for Optical Components

As a factory specializing in CNC Machining Services, we once received a project for high-precision optical instrument parts (optical mounts). This case perfectly illustrates the importance of choosing the correct temper.

Customer Requirement: The customer required the parts to be made of 6061 aluminum alloy and must reach T6 level strength. At the same time, tolerances were strictly controlled within ±0.01mm, and the requirements for flatness were extremely high.

VMT’s Professional Solution: During initial communication, the customer asked if they could first machine the parts in the "Annealed (O state)" and then reach T6 strength through heat treatment. Due to the specificity of optical parts, it was obvious that precision requirements were more important than high strength requirements. We re-confirmed the details with the customer (precision ±0.01mm, surface roughness Ra 0.6). Regarding this, our engineers suggested: directly performing precision CNC machining on 6061-T651 pre-stretched plates.

• Reason 1: Avoid Heat Treatment Deformation. If quenching and aging (T6 treatment) are performed after machining, the material will undergo drastic temperature changes, causing unpredictable expansion or distortion of the parts, and precision tolerances will vanish.
• Reason 2: Dimensional Stability. We chose 6061-T651 instead of ordinary T6. The suffix "51" indicates that the material has undergone controlled mechanical stretching to eliminate residual stress. This means that during the cutting process, the parts will not "rebound" or deform due to stress release. (T651 sacrifices only a small portion of strength compared to T6 but brings high dimensional stability).
  

Final Result: By directly cutting the T651 state material, VMT successfully delivered this batch of optical parts. Not only did the strength meet the standard, but the dimensional stability was excellent, avoiding the risk of scrapping due to secondary heat treatment.

FAQs

Q1: What is the temper for aluminum? 

A: It represents the condition or hardness of the aluminum alloy. It indicates whether the material has been cold-worked, heat-treated, or naturally aged to achieve its final mechanical properties.

Q2: Does aluminum need to be tempered? 

A: Yes. Raw aluminum (F or O state) is usually too soft for structural use. Tempering aluminum significantly increases its hardness, yield strength, and fatigue resistance.

Q3: What does a 6061 T6 temper indicate? 

A: 6061-T6 indicates the alloy has been solution heat-treated and then artificially aged. It is the "sweet spot" for 6061, balancing high strength with excellent machinability.

Q4: What is H18 temper aluminum? 

A: H18 stands for "Full Hard." It is the state where the highest strength is achieved through strain hardening, typically used for foils or sheets where high strength is needed but bending is minimal.

Q5: What is the difference between H19 and H18 aluminum? 

A: H19 is "Extra Hard," with a tensile strength even higher than H18. It is typically used for extremely thin, high-strength aluminum foil production.

Q6: What is 6063 T6 aluminum used for? 

A: Compared to T5, 6063-T6 has higher strength. it is commonly used for precision extrusions that must bear loads, such as automation equipment frames and sports equipment components.