6061 T6 vs. 6061 T651: Exploring the Key Differences

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6061 T6 vs. 6061 T651: Exploring the Key Differences

When it comes to aluminum alloys, 6061 is a popular choice for a variety of applications due to its excellent strength-to-weight ratio, good machinability, and weldability. Within the 6061 alloy, there are two common tempers that are often compared and contrasted: 6061-T6 and 6061-T651. Both of these tempers have their own unique properties and advantages, making them suitable for different uses. In this article, we will explore the key differences between 6061-T6 and 6061-T651 to help you decide which one is right for your project.


6061-T6 is a solution heat-treated and artificially aged temper of the 6061 alloy. This temper is achieved by heating the alloy to a high temperature and then quenching it in cold water, which results in a stable material with good machinability and weldability. The T6 temper is often used in applications where high strength is required, such as in aerospace, marine, and automotive industries.

One of the key characteristics of 6061-T6 is its high tensile strength, making it ideal for structural components that need to withstand heavy loads. The hardness of this temper is around 95 HB, which means it is relatively easy to machine and shape. Additionally, 6061-T6 has good corrosion resistance, making it suitable for outdoor and marine applications.

However, one potential drawback of 6061-T6 is its susceptibility to stress corrosion cracking, which can occur when the material is exposed to certain environments. To mitigate this risk, it is important to properly store and maintain components made from 6061-T6.


6061-T651 is a stress-relieved temper of the 6061 alloy, achieved by stretching the material to remove internal stresses. This temper is often used in applications where dimensional stability is crucial, such as in precision components and tooling. The T651 temper is known for its excellent machinability and formability, making it a popular choice for machining and shaping operations.

One of the key advantages of 6061-T651 is its improved flatness and stability compared to the T6 temper. The stress-relieved process helps to minimize distortion and warping during machining, resulting in more accurate and consistent parts. This temper also has slightly lower tensile strength compared to T6, but it retains good mechanical properties and corrosion resistance.

It is important to note that the stress-relieved process of 6061-T651 can affect the material’s hardness and strength properties. While the tensile strength may be slightly lower than T6, the overall performance of 6061-T651 is still suitable for a wide range of applications.

Key Differences

Now that we have explored the characteristics of 6061-T6 and 6061-T651, let’s summarize the key differences between these two tempers:

1. Strength: 6061-T6 has higher tensile strength compared to 6061-T651, making it suitable for applications where high strength is required.

2. Machinability: 6061-T651 has slightly better machinability and formability compared to 6061-T6, thanks to its stress-relieved process.

3. Dimensional Stability: 6061-T651 offers improved flatness and stability, making it ideal for precision components and tooling.

4. Corrosion Resistance: Both tempers exhibit good corrosion resistance, but proper storage and maintenance are essential to prevent stress corrosion cracking in 6061-T6.

In conclusion, the choice between 6061-T6 and 6061-T651 will depend on the specific requirements of your project. If you need high strength and toughness, 6061-T6 is a good option. On the other hand, if dimensional stability and machinability are paramount, 6061-T651 may be the better choice. Whichever temper you choose, both 6061-T6 and 6061-T651 are versatile and reliable materials that can deliver excellent performance in a wide range of applications.

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