Whether it’s the frame of the bicycle you ride every day, a complex aerospace component flying thousands of feet above the ground, or the sleek housing of an electronic device on your wrist, there’s a good chance you’ll find 6061-T6 aluminum somewhere inside. Its popularity is no accident. Few engineering materials offer such a well-balanced combination of strength, machinability, corrosion resistance and affordability.
In fact, 6061-T6 is so common that it has become a standard stock material in virtually every machine shop, prototype manufacturer, and contract manufacturing facility. If you’ve ever ordered a CNC machined prototype, the first material recommendation you got was aluminum 6061-T6.
What is Aluminum 6061？
The 6000 series aluminum alloys are aluminum-magnesium-silicon (Al-Mg-Si) alloys. Their strengthening phase is Mg₂Si. These alloys belong to the family of heat-treatable aluminum alloys, and they offer a good balance of strength, corrosion resistance, weldability, and formability. Among the 6000 series alloys, 6061 and 6063 are the most widely used grades. Aluminum 6061 is popular for CNC machining, while 6063 is popular for architectural and industrial aluminum extrusion.
Aluminum 6061 is a heat-treatable Al-Mg-Si alloy whose nominal chemical composition includes 0.8–1.2% magnesium, 0.4% to 0.8% silicon, 0.15% to 0.40% copper, and 0.04% to 0.35% chromium by weight. The strengthening constituent is the Mg₂Si precipitate formed during age hardening. Copper is added to increase the alloy’s mechanical strength, while chromium is introduced to offset the reduction in corrosion resistance caused by copper and to improve microstructural stability. Because aluminum 6061 has relatively high quench sensitivity, it requires a carefully controlled heat-treatment process to achieve optimum mechanical properties. After extrusion, the alloy is typically subjected to solution heat treatment, rapid quenching, and artificial aging to develop the desired strength and hardness.
T6 Temper of Aluminum 6061
The strength of aluminum 6061 is derived from heat treatment. Through a combination of solution heat treatment and aging, alloying elements such as magnesium and silicon precipitate from the aluminum matrix and form fine Mg₂Si strengthening particles. These precipitates significantly increase the alloy’s mechanical strength while maintaining its excellent corrosion resistance, machinability, and weldability.
T6 is the most common condition among all temper conditions. The designation “T6” indicates that the alloy has been solution heat treated and then artificially aged to achieve its optimum balance of properties.
As shown in the figure below, the T6 temper typically delivers the higher strength level without sacrificing the key characteristics that make 6061 attractive for engineering applications. Decades of industrial experience have demonstrated that the mechanical properties achieved in the T6 condition are sufficient for the vast majority of structural, automotive and aerospace applications. This combination of performance, availability, and cost-effectiveness is a major reason why 6061-T6 has become the commonly specified aluminum alloy.
Other Temper Designations of Aluminum
Heat-treatable aluminum alloys commonly use a temper designation consisting of the letter “T” followed by one or more numbers. The “T” indicates that the material has undergone thermal treatment to produce stable mechanical properties. Different numbers mean different combinations of heat treatment, aging, and cold working processes.
| Temper | Description |
|---|---|
| T1 | Cooled from an elevated-temperature shaping process and naturally aged to a substantially stable condition. |
| T2 | Cooled from an elevated-temperature shaping process, cold worked, and naturally aged. |
| T3 | Solution heat treated, cold worked, and naturally aged. |
| T4 | Solution heat treated and naturally aged to a stable condition. |
| T5 | Cooled from a high-temperature forming process and then artificially aged. |
| T6 | Solution heat treated and artificially aged. |
| T7 | Solution heat treated and overaged (stabilized). |
| T8 | Solution heat treated, cold worked, and artificially aged. |
| T9 | Solution heat treated, artificially aged, and then cold worked. |
| T10 | Cooled from an elevated-temperature shaping process, cold worked, and artificially aged. |
Mechanical Properties of Aluminum 6061 T6
| Property | Metric |
|---|---|
| Ultimate Tensile Strength | 290 ~ 310 MPa |
| Yield Strength (0.2%) | 240 ~ 276 MPa |
| Shear Strength | 207 MPa |
| Fatigue Strength (10⁷ cycles) | 96 MPa |
| Elongation | 8 ~ 12 % |
| Modulus of Elasticity | 69 ~ 70 GPa |
| Shear Modulus | 26 GPa |
| Brinell Hardness | 95 HB/107 HV |
Physical Properties of Aluminum 6061 T6
| Property | Value |
|---|---|
| Density | 2.70 g/cm³ |
| Crystal Structure | FCC structure |
| Melting Range | 582 ~ 652 °C |
| Electrical Resistivity | 0.039 ~ 0.040 μΩ·m |
| Electrical Conductivity | 40 ~ 43 % IACS |
| Elastic Modulus | 69 ~ 70 GPa |
| Poisson’s Ratio | 0.33 |
Thermal Properties of Aluminum 6061 T6
| Property | Value |
|---|---|
| Thermal Conductivity | 166 ~ 167 W/m·K |
| Specific Heat Capacity | 896 J/kg·K |
| Thermal Expansion Coefficient | 23.3 ~ 23.6 ×10⁻⁶ /K |
| Thermal Diffusivity | 68 mm²/s |
| Solidus Temperature | 582 °C |
| Liquidus Temperature | 652 °C |
Corrosion Resistance of Aluminum 6061 T6
| Environment | Rating |
|---|---|
| Atmospheric | Excellent |
| Fresh Water | Excellent |
| Industrial Atmosphere | Good |
| Stress Corrosion Cracking | Very Good |
| Pitting Corrosion | Moderate |
| Crevice Corrosion | Moderate |
Aluminum 6061 T6 Plate
T6 is the most common temper of 6061 aluminum plate. For 6061 medium or thick plates, the T6 temper is achieved through a process that includes solution heat treatment, plate cutting, stretching, artificial aging, sawing, surface finishing, and packaging. The entire production cycle generally takes approximately 10 days.
After solution heat treatment, no additional cold working is required. Straightening and leveling operations may be performed if necessary, provided they do not adversely affect the mechanical properties of the material.
Other aluminum 6061 plates include 6061-F and 6061-O aluminum plates:
The 6061-F aluminum plate is the as-fabricated condition of 6061 aluminum plate. It is suitable for products with special requirements related to work hardening or subsequent heat treatment during forming operations. Under normal production scheduling, shipment can typically be completed within three days. Mechanical properties are not specified for the F temper. Customers may perform their own heat treatment processes to convert the material into the desired temper for specific applications. As a result, F-temper 6061 aluminum plate is generally the most economical option among the available tempers.
The 6061-O aluminum plate is the fully annealed condition of 6061 aluminum alloy and provides the lowest strength level among all tempers.It is primarily used for thin sheets with thicknesses below 8.0 mm, where excellent formability is required. The production cycle of O-temper material is generally shorter than that of T6 temper but longer than that of F temper. Due to the complete annealing process, O-temper 6061 aluminum plate offers maximum ductility and formability, making it particularly suitable for applications involving bending, deep drawing, and complex forming operations.
