6061 aluminum is one of the most flexible and widely used aluminum alloys, known for its fantastic mechanical properties and corrosion resistance. Among the different 6061 tempers, 6061-T6 and 6061-T651 stand out for their strength and suitability for a range of applications.

At Yijin Hardware, we know how important it is to understand the differences between these two tempers, especially when it comes to choosing the ideal material for specific engineering needs. Here’s our detailed comparison for 6061 T6 vs. T651.

Key Takeaways

• 6061-T6 is solution heat-treated and artificially aged, which provides high strength but may retain some residual stress.
• 6061-T651 includes an additional stretching process for improved dimensional stability and reduced internal stresses.
• Both tempers show similar mechanical properties, including yield strength and tensile strength, but differ in machinability.
• The choice between T6 and T651 depends on application requirements, mainly regarding precision and stability.
• 6061 aluminum alloys are widely used in aerospace, automotive, and marine industries.

What is 6061-T6?

6061-T6 is a specific temper designation of the 6061 aluminum alloy that has gone through an intense heat treatment process. The T6 temper involves solution heat treatment followed by artificial aging. During the solution heat treatment, the aluminum billet is heated to around 495 °C (925 °F) and then quickly quenched in water. This process dissolves the alloying elements, mainly magnesium and silicon, creating a supersaturated solid solution.

After quenching, the material is artificially aged at a lower temperature (around 120 to 180 °C or 250 to 360 °F) for about 8 hours. This aging process precipitates the alloying elements from the solid solution, improving the mechanical properties of the alloy. The result is an aluminum alloy with fantastic tensile strength, yield strength, and hardness. However, while T6 provides high strength, it might also retain some residual stresses from the heat treatment process.

Benefits of 6061-T6 Aluminum

• High Strength: The T6 temper offers a tensile strength of approximately 310 MPa (45 ksi) and a yield strength of around 276 MPa (40 ksi), making it suitable for structural applications.
• Corrosion Resistance: 6061-T6 shows good resistance to corrosion, which is important for applications exposed to harsh environments.
• Weldability: This temper allows for good weldability, although preheating may be necessary to minimize cracking during welding processes.
• Versatility: Its properties make it great for various applications, including automotive parts, marine structures, and aerospace components.

What is 6061-T651?

6061-T651 is another temper designation of the same aluminum alloy, but with an extra processing step that improves its performance characteristics. Like T6, T651 goes through solution heat treatment followed by artificial aging.

However, after aging, T651 involves an extra step where the material is stretched or straightened at room temperature to relieve residual stresses. This stretching process helps improve dimensional stability and flatness while reducing internal stresses that could lead to warping or distortion during machining. As a result, T651 is great for applications requiring precise dimensions and tight tolerances.

Benefits of 6061-T651 Aluminum

• Improved Dimensional Stability: The stretching process in T651 reduces residual stresses compared to T6, allowing for better dimensional control in machined parts.
• Higher Machinability: T651 offers better machinability due to its reduced internal stresses, making it easier to cut and shape without deformation.
• Tighter Tolerances: This temper is preferred in applications where precision is important, such as in aerospace components or intricate machined parts.
• Similar Strength Properties: Although it undergoes extra processing, T651 maintains similar tensile and yield strengths as T6.

6061-T6 vs. 6061-T651: What are the Main Differences?

We’ve outlined the major differences between 6061-T6 and 6061-T651 aluminum below:

While both 6061-T6 and 6061-T651 share many similarities due to their common alloy composition, they are quite different in their processing methods and ultimate properties. Let’s compare them!

Heat Treatment Processes

The main difference lies in their heat treatment processes. Both tempers begin with solution heat treatment followed by artificial aging. However, T651 includes an extra step where the material is stretched after aging. This extra step helps relieve residual stresses that can affect performance during machining operations.

Mechanical Properties

Both 6061-T651 and 6061-T6 tempers have similar mechanical properties; for example:

• Tensile Strength: Approximately 310 MPa (45 ksi) for both
• Yield Strength: Around 276 MPa (40 ksi) for both

However, due to the stress-relieving step in T651, it tends to show better performance under machining conditions compared to T6. It’s also worth noting that their strength will vary depending on thickness.

Dimensional Stability

Another difference between T6 aluminum and T651 is in dimensional stability. 6061-T651 aluminum has better dimensional stability due to its additional stretching process. This characteristic makes it preferable in applications requiring dimensional stability or high precision where any warping or distortion could be detrimental in comparison to 6061-T6 aluminum.

Machinability

Machinability is another area where T651 stands out compared to aluminum 6061-T6. The reduced residual stresses in T651 allow for more straightforward machining processes without compromising the integrity of the material. This makes T651 a better choice when weighing up 6061-T6 and 6061-T651 in industries that rely heavily on precision machining techniques.

Application Suitability

Both T6 and T651 tempers have multiple uses across various industries. However, they are more suitable for certain applications:

• T6 is often used in applications where high strength is important, but precise dimensions are less essential.
• T651, on the other hand, is best for applications requiring tight tolerances and high accuracy — common in aerospace components where safety and reliability are crucial.

Yijin Hardware: Aluminum Tempers CNC Machining Services

Understanding the differences when weighing up T651 vs. T6 aluminum tempers can significantly impact material selection for engineering projects. While both offer great mechanical properties suitable for various applications, choosing between them depends on specific needs such as dimensional stability and machinability.

If you’re looking for high-quality CNC machining services tailored to your needs with expertise in aluminum tempers like T6 and T651, reach out to Yijin Hardware!

FAQs on 6061 T6 vs. T651 | 6061 Tempers, Aluminum Properties Comparison

What is the stiffness of 6061 aluminum?

The stiffness of 6061 aluminum, specifically in the T6 temper, is approximately 69 GPa (10,000 ksi), which is suitable for many structural applications. This stiffness is generally lower than that of 7075 aluminum, making 6061 a more ductile option.

What is the temperature range of 6061?

The temperature range of 6061 aluminum for its mechanical properties typically extends from -320 °F to around 400 °F, depending on the specific temper and application. It’s important to consider that heat-treated and stress-relieved 6061 may show different performance characteristics within this range.

Is T651 good for making small bends (angles less than 45 degrees)?

T651 is generally suitable for making small bends, including angles less than 45 degrees, due to its good ductility. However, it’s essential to ensure the proper surface finish and bend radius to avoid cracking, especially when considering anodize treatment after bending.

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