Aluminum alloys are widely used across industries due to their lightweight nature, corrosion resistance, and excellent mechanical properties. Among the many options available, 6061 aluminum is one of the most versatile and popular choices. Known for its strength, machinability, and weldability, 6061 is commonly used in aerospace, automotive, construction, and marine applications.
Within the 6061 alloy family, two temper designations often cause confusion: 6061 T651 and 6061 T6 aluminum sheet. Both offer outstanding performance, but they are not identical. Understanding their similarities and differences helps engineers, buyers, and manufacturers make the right selection for their projects.
What Does Temper Mean in Aluminum?
The term temper refers to the mechanical and thermal treatment applied to aluminum to achieve specific mechanical properties. In the case of 6061, the base alloy is heat-treated and aged to enhance its strength and durability.
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T6: Solution heat-treated and artificially aged.
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T651: Solution heat-treated, stress-relieved by stretching, and artificially aged.
This slight variation in processing leads to differences in performance, machining behavior, and final applications.
What is 6061 T6 Aluminum Sheet?
6061 T6 is the standard temper for 6061 aluminum. It is widely recognized for its excellent strength-to-weight ratio and balanced properties.
Key Features
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High tensile and yield strength.
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Good corrosion resistance in most environments.
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Excellent machinability and weldability.
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Lightweight yet durable.
Applications
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Aerospace and automotive parts.
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Structural components in bridges and towers.
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Marine fittings and shipbuilding.
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Pressure vessels and pipelines.
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Industrial machinery and tools.
What is 6061 T651 Aluminum Sheet?
6061 T651 is essentially the same alloy as 6061 T6 but undergoes an additional stress-relieving process. After solution heat treatment and artificial aging, the material is stretched to relieve residual stresses introduced during heat treatment.
Key Features
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Superior dimensional stability compared to T6.
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Reduced risk of warping or distortion during machining.
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Same corrosion resistance and strength as T6.
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Preferred for precision machining applications.
Applications
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Aerospace tooling and jigs.
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High-precision automotive components.
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Machine frames and fixtures.
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Structural parts requiring tight tolerances.
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Defense and heavy engineering equipment.
6061 T651 vs. 6061 T6: Key Differences
1. Manufacturing Process
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6061 T6: Heat-treated and artificially aged.
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6061 T651: Same as T6 but stretched to relieve internal stresses.
2. Residual Stress
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T6: May retain internal stresses, leading to slight distortion during machining.
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T651: Stress-relieved, ensuring greater dimensional stability.
3. Machinability
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T6: Good machinability but may warp under heavy machining.
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T651: Excellent machinability with less distortion, ideal for precision parts.
4. Mechanical Properties
Both tempers have very similar strength and corrosion resistance. For most general applications, the mechanical properties are nearly identical.
5. Cost
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T6: Generally less expensive.
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T651: Slightly higher cost due to the additional stress-relieving step.
6. Applications
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T6: More common for structural and general-purpose uses.
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T651: Preferred for machining-intensive and precision-critical applications.
Mechanical Properties Comparison
| Property | 6061 T6 | 6061 T651 |
|---|---|---|
| Tensile Strength (MPa) | ~290 | ~290 |
| Yield Strength (MPa) | ~240 | ~240 |
| Elongation (%) | 8–12 | 8–12 |
| Hardness (Brinell HB) | ~95 | ~95 |
As shown above, the mechanical strength is nearly identical, with the primary difference being stress relief in T651.
Which One Should You Choose?
Choose 6061 T6 If:
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Your project requires strong, lightweight material for structural applications.
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Cost is an important factor.
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The part does not require extensive machining.
Choose 6061 T651 If:
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Precision machining is required.
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Warping or distortion during machining must be avoided.
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The project demands dimensional stability and tight tolerances.
Industry Standards
Both 6061 T6 and T651 sheets are produced under strict international standards:
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ASTM B209: Standard specification for aluminum sheet and plate.
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AMS 4027 / AMS 4029: Aerospace specifications for 6061 sheet and plate.
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EN 485: European standards for aluminum alloys.
Compliance ensures consistent quality and mechanical performance.
Environmental Considerations
Like most aluminum alloys, both 6061 T6 and T651 are fully recyclable. The choice between them does not affect sustainability, but precision machining with T651 may reduce material waste caused by distortions.
Future Trends
With industries increasingly demanding lightweight, durable, and precise materials, the popularity of 6061 aluminum in both T6 and T651 tempers will continue to grow. Emerging trends include:
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Hybrid Structures: Combining aluminum with composites for aerospace.
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Green Manufacturing: Lower-carbon aluminum production processes.
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Digital Machining: CNC technologies making use of T651’s stress-relieved stability.
Conclusion
Both 6061 T6 and 6061 T651 aluminum sheets are high-performance materials widely used in engineering and manufacturing. While they share similar strength and corrosion resistance, the key difference lies in residual stress management. T6 is suitable for most structural applications, while T651 is the preferred option when precision machining and dimensional stability are required.
For buyers and engineers, choosing between them depends on application requirements, budget, and machining needs.
As a trusted supplier of aluminum products, sasaaluminum offers high-quality 6061 T6 and T651 sheets that meet international standards. With a commitment to reliability and customer satisfaction, sasaaluminum ensures that industries receive materials that perform consistently under demanding conditions.
By making the right material choice, companies can optimize performance, reduce costs, and enhance product longevity.
Post time: Sep-01-2025