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T6 VS T651

Aluminum alloys T6 vs T651 tempers are both heat-treated to enhance their mechanical properties, offering high strength, a lightweight structure, and resistance to corrosion, which are critical for a wide array of industrial applications.

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T6 VS T651

Aluminum alloys are widely used in various industries due to their excellent strength-to-weight ratio, corrosion resistance, and versatility. Among the many temper designations, T6 VS T651 are two common heat treatments applied to aluminum alloys, particularly in the 6000 series like 6061 and 6063.

Aluminum alloys T6 vs T651 tempers are both heat-treated to enhance their mechanical properties, offering high strength, a lightweight structure, and resistance to corrosion, which are critical for a wide array of industrial applications.

Aluminum t6 vs t651

Aluminum t6 vs t651

Here’s a detailed comparison:

T6 Temper

  • Definition: T6 is a heat treatment that involves solution heat treatment followed by artificial aging.
  • Process:
    1. Solution Heat Treatment: The aluminum is heated to a high temperature (around 520°C to 550°C) and held there for a specific time to dissolve the alloying elements uniformly into the aluminum matrix.
    2. Quenching: The metal is then rapidly cooled, or quenched, usually in water, to trap the alloying elements in a supersaturated solid solution.
    3. Artificial Aging: Finally, the material is heated to a lower temperature (around 160°C to 180°C) for several hours to allow the alloying elements to precipitate out, forming a fine dispersion of precipitates that increase strength.
  • Properties:
    • Strength: Provides high strength due to the formation of precipitates during aging.
    • Ductility: Generally has good ductility but can be less ductile than T651 due to potential residual stresses.
    • Stress: Can have internal stresses that might cause distortion during machining or after stress-relief operations.
  • Applications: Used in applications where high strength is required without the need for extensive machining or where the final shape does not require flatness or straightness to be maintained.

T651 Temper

  • Definition: T651 is similar to T6 but includes an additional stress-relieving step to minimize distortion.
  • Process:
    1. Solution Heat Treatment: Same as T6.
    2. Quenching: Same as T6.
    3. Artificial Aging: Same as T6.
    4. Stress Relieving: After aging, the aluminum is subjected to a controlled amount of cold working (usually by stretching) to relieve internal stresses. This is followed by a slight re-aging to stabilize the material.
  • Properties:
    • Strength: Retains the high strength of T6 but with improved stress distribution.
    • Ductility: Tends to have better ductility due to the stress-relieving process, which reduces internal stresses.
    • Flatness and Straightness: Provides better flatness and straightness because of the stretching process, making it ideal for parts requiring tight tolerances in these aspects.
  • Applications: Preferred for applications where precision in shape, flatness, and straightness is crucial, such as in aerospace components, structural parts, and where extensive machining is required.

Key Differences

Aspect T6 T651
Process Heat treatment only Heat treatment + Stress relieving through cold work
Strength High strength High strength with better stress distribution
Ductility Good, but can be less due to residual stresses Better due to stress relief
Flatness/Straightness Can have issues with flatness due to internal stresses Improved flatness and straightness due to stretching
Machinability Can be prone to distortion during machining Less prone to distortion, better for precision work
Applications General strength applications Precision parts, aerospace, structural components

Which aluminum alloys have T tempering?

In the heat treatment of aluminum alloys, T series tempering state (Temper Designations) refers to the state of changing the mechanical properties and physical characteristics of aluminum alloys through heat treatment. Only alloys that can pass heat treatment have T tempering state, such as 2000 series, 6000 series, 7000 series alloys, common ones are 2219, 2024, 6061, 6063, 7005, 7075, etc.

Here is a simple comparison table for the aluminum alloys 2219, 2024, 6061, 6063, 7005, and 7075:

Alloy Composition Strength Corrosion Resistance Weldability Machinability Heat Treatability Typical Applications
2219 Copper (Cu): 6.3%, Iron (Fe): 0.3%, Manganese (Mn): 0.3%, Titanium (Ti): 0.06% High Moderate Good Fair T6 Aerospace, cryogenic applications, structural components
2024 Copper (Cu): 4.4%, Magnesium (Mg): 1.5%, Manganese (Mn): 0.6%, Iron (Fe): 0.5% Very High Poor Poor Excellent T3, T4, T8 Aircraft structures, aerospace, high-strength fasteners
6061 Magnesium (Mg): 1.0%, Silicon (Si): 0.6%, Copper (Cu): 0.28% Medium to High Good Excellent Good T6, T651 Structural components, automotive parts, bicycle frames
6063 Magnesium (Mg): 0.7%, Silicon (Si): 0.4% Medium Excellent Excellent Good T5, T6 Extrusions, architectural applications, window frames
7005 Zinc (Zn): 4.5%, Magnesium (Mg): 1.4%, Manganese (Mn): 0.45% High Good Good Fair T5, T6 Bicycle frames, structural applications requiring high strength and toughness
7075 Zinc (Zn): 5.6%, Magnesium (Mg): 2.5%, Copper (Cu): 1.6% Very High Moderate to Poor Poor Fair T6, T73, T76 Aerospace components, high-stress applications, military equipment

Notes:

  • Strength: Refers to the alloy’s tensile strength, with “Very High” indicating the highest strength among the listed alloys.
  • Corrosion Resistance: Ranges from poor to excellent, influenced by the alloying elements and their proportions.
  • Weldability: Indicates how well the alloy can be welded. Poor weldability means special precautions or techniques might be needed.
  • Machinability: Refers to how easily the alloy can be machined. “Excellent” means it can be machined with minimal tool wear and high speed.
  • Heat Treatability: The common heat treatments applied to enhance the alloy’s properties. T6 is a common heat treatment involving solution heat treatment followed by artificial aging.
  • Typical Applications: Shows some of the primary uses for each alloy, reflecting their unique characteristics and performance in specific environments or applications.

This table provides a quick overview, but each alloy’s performance can vary based on specific heat treatments, thickness, and manufacturing processes applied.

Conclusion

The choice between T6 and T651 aluminum alloy depends on the specific requirements of the application:

  • T6 is ideal for components where high strength is the primary concern, and the final shape or flatness isn’t critical.
  • T651 is chosen when both strength and dimensional stability are important. The additional stress relief step in T651 makes it suitable for applications where precision in flatness, straightness, or where extensive machining is required.

Both tempers offer excellent properties for aluminum alloys, but understanding their differences allows for more informed decisions in material selection, ensuring that the aluminum part meets the design specifications and performance expectations.

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