6061 aluminum alloy is a versatile and frequently used material renowned for its superior mechanical qualities and corrosion resistance. The several tempers of 6061 aluminum, 6061-T651, 6061-T6, and 6061-T6511, each provide distinct advantages customized to certain applications and part geometries. Understanding the differences between these tempers is critical for determining the best material for certain engineering and production requirements.
Aluminum 6061-T6, -T651, and -T6511 Explained
What Is 6061-T6?
The "T6" designation refers to the temper or heat treatment applied to the aluminum. For 6061-T6, this involves solution heat treatment followed by artificial aging. During solution heat treatment, the aluminum is heated above its solvus temperature, allowing the alloying elements to form a uniform solid solution. Artificial aging then completes the T6 process, enhancing the material's strength and hardness. According to industry standards, 6061-T6 is generally available in thicknesses below 0.25".
What Is 6061-T651?
6061-T651 is a widely used structural aluminum alloy in plate form. It undergoes the same solution heat treatment and artificial aging as T6 to develop strengthening precipitates, making it stronger and harder than the untreated alloy. Additionally, the material is stretched after heat treatment to relieve internal stresses, reducing warping and distortion during machining. The "5" indicates a slight reduction in hardness compared to standard T6. T651 plates are typically at least 0.25" thick.
What Is 6061-T6511?
6061-T6511 refers to extruded bars or rods that receive the same T6 heat treatment, along with stress relief and, in some cases, straightening. Extrusions certified to T6511 temper are often dual-certified to T6 via a mill test report. T6511 is generally more cost-effective than T651 stock.
Differences Between 6061-T651, 6061-T6, and 6061-T6511
6061-T651:
Primarily used as plate stock; cold-finished bars can also be classified as T651.
Offers the highest strength of the three due to the additional stretching (cold working) during processing.
Less formable or workable compared to the other tempers.
Ideal for demanding structural applications requiring maximum strength.
Low residual stress ensures dimensional stability and minimizes warping in large, flat parts.
Uniform grain structure provides consistent appearance and finish.
Versatile due to wide size availability and mechanical properties, though generally more expensive.
6061-T6:
Typically available as sheet stock, with a maximum thickness below 0.25".
Medium strength – stronger than untreated 6061, but not as strong as T651.
More formable than T651, offering a good balance of strength and workability.
T6511 extruded bars can sometimes be dual-certified to T6.
Suitable for general applications where both strength and formability are important, but size availability is limited.
6061-T6511:
Commonly supplied as extruded bars or rods.
Most formable and workable of the three tempers.
Ideal for machined or turned aluminum components when maximum hardness, thickness, or stability is not required.
For stock thicker than 1", available widths are limited, generally below 15".
Interchangeability of 6061-T6 and T6511
6061-T6 and T6511 can sometimes be dual-certified, as noted on material certifications. Due to their differences, orders specifying 6061-T6 may be fulfilled using 6061-T6511, but not with 6061-T651.
GNEE supplies all these 6061 aluminum tempers, providing options to meet various structural and machining requirements.
