Overview of 6061 Aluminum Plate
6061 aluminum plate is a magnesium-silicon alloy valued for its excellent mechanical strength, corrosion resistance and machinability. It is widely used in aerospace, transportation, tooling and structural applications. Different tempers adjust internal stress, strength and formability, making 6061 suitable for a wide range of part geometries. The three tempers most commonly compared are 6061-T6, 6061-T651 and 6061-T6511.
What Is 6061-T6 Aluminum Plate?
The T6 temper refers to solution heat treatment followed by artificial aging. During solution heat treatment, the alloy is heated above the solvus temperature so the alloying elements dissolve evenly into the aluminum matrix; artificial aging then strengthens the material by forming fine precipitates.
Key features of 6061-T6 plate include good strength and hardness, balanced machinability and formability, and common availability in thinner plate and sheet forms, typically below 6.35 mm (0.25 inch). This temper is often selected for general-purpose structural and machined components.
What Is 6061-T651 Aluminum Plate?
6061-T651 undergoes the same heat treatment as T6 but includes an additional stress-relieving stretch after solution heat treatment. The controlled stretching reduces internal residual stress, improving dimensional stability during machining, while meeting the same strength requirements as T6.
Characteristics of 6061-T651 plate include supply mainly as plate stock, a minimum thickness typically of 6.35 mm (0.25 inch) or more, excellent flatness stability and consistent machined-part accuracy. Because of its stability and strength, 6061-T651 is widely used for large, flat, precision-machined parts such as fixture plates, mold bases and machine tables.
What Is 6061-T6511 Aluminum?
6061-T6511 is typically supplied as an extruded bar or rod rather than a rolled plate. It receives the same heat treatment as T6, followed by stress relief and straightening. Key points are that it comes in extruded bar or rod form, is stress-relieved for improved straightness, is often dual-certified to meet T6 requirements, generally costs less than T651 plate, and offers greater formability than T651.
For applications that do not require the flatness and residual stress control of plate stock, T6511 is a cost-effective alternative. Note that the T6511 designation belongs to the extruded product family, so it should be compared with plate forms only in terms of the mechanical requirements of the part.
Temper Comparison
6061-T651 plate offers the highest dimensional stability and is the preferred choice for precision-machined plates and large flat parts, with strength equal to T6 and the best residual stress control of the three forms. 6061-T6 sheet and thin plate offers medium strength with moderate formability and good stability, suiting general structural and machined components. 6061-T6511 extruded bar and rod offers medium strength with the highest formability of the three and moderate stability, suiting turned parts and general machining.
In many cases, 6061-T6511 extrusions are dual-certified to meet T6 requirements, as shown on mill test reports. However, 6061-T651 plate is not a direct substitute where T6 sheet is specified, because the product forms and processing differ.
Chemical Composition and Mechanical Properties
The typical composition of 6061 is magnesium 0.80-1.20%, silicon 0.40-0.80%, copper 0.15-0.40%, chromium 0.04-0.35%, iron up to 0.70%, zinc up to 0.25% and titanium up to 0.15%, with the balance aluminum.
Typical mechanical properties for 6061-T6 plate are a tensile strength of about 310 MPa (45 ksi), a yield strength of about 240 MPa (35 ksi) minimum, elongation of 8-12%, hardness of about 95 HB and a density of 2.70 g/cm3. Certified minimums follow the governing standard such as ASTM B209 and vary with thickness.
Common Size Range
6061 plate is commonly supplied in thicknesses from 6 mm to 150 mm, widths up to 2600 mm and lengths up to 12000 mm, with custom sizes available on request.
How to Choose the Right Temper
Select 6061-T6 for general-purpose sheet and thin-plate parts where a balance of strength and workability is sufficient. Select 6061-T651 for machined plate components that must hold flatness and dimensional accuracy after material removal. Select 6061-T6511 for extruded bars and rods used in turned and machined parts where the lower cost and better formability of extrusion are advantageous.
FAQ
Q: What is the difference between T6 and T651?
A: Both are solution heat-treated and artificially aged. T651 includes an additional controlled stretch after solution heat treatment that relieves residual stress for better dimensional stability during machining; strength requirements are the same.
Q: Can T6511 extrusions meet T6 requirements?
A: Yes, 6061-T6511 extruded bar and rod is often dual-certified to meet T6 mechanical requirements, as documented on the mill test report.
Q: Which temper is best for CNC machined plates?
A: 6061-T651 is the standard choice for machined plate because the stress relief keeps the material stable and flat during material removal.
Q: What thicknesses are available for 6061-T651 plate?
A: 6061-T651 plate is typically supplied from 6.35 mm (0.25 inch) upward, commonly from 6 mm to 150 mm, with widths up to 2600 mm and lengths up to 12000 mm.
Q: Is T6 or T651 stronger?
A: They meet the same strength requirements. T651 differs in processing, not in strength: the stretch step improves residual stress and dimensional stability.
