6061 aluminium alloy
|Density (ρ)||2.70 g/cm3|
|Young's modulus (E)||68.9 GPa (9,990 ksi)|
|Tensile strength (σt)||124–290 MPa (18.0–42.1 ksi)|
|Elongation (ε) at break||12–25%|
|Poisson's ratio (ν)||0.33|
|Melting temperature (Tm)||585 °C (1,085 °F)|
|Thermal conductivity (k)||151–202 W/(m·K)|
|Linear thermal expansion coefficient (α)||2.32×10−5 K−1|
|Specific heat capacity (c)||897 J/(kg·K)|
|Volume resistivity (ρ)||32.5–39.2 nOhm·m|
6061 is a precipitation-hardened aluminum alloy, containing magnesium and silicon as its major alloying elements. Originally called "Alloy 61S", it was developed in 1935. It has good mechanical properties, exhibits good weldability, and is very commonly extruded (second in popularity only to 6063). It is one of the most common alloys of aluminum for general-purpose use.
It is commonly available in pre-tempered grades such as 6061-O (annealed), tempered grades such as 6061-T6 (solutionized and artificially aged) and 6061-T651 (solutionized, stress-relieved stretched and artificially aged).
The alloy composition of 6061 is:
- Silicon minimum 0.4%, maximum 0.81% by weight
- Iron no minimum, maximum 0.7%
- Copper minimum 0.15%, maximum 0.4%
- Manganese no minimum, maximum 0.15%
- Magnesium minimum 0.8%, maximum 1.2%
- Chromium minimum 0.04%, maximum 0.35%
- Zinc no minimum, maximum 0.25%
- Titanium no minimum, maximum 0.15%
- Other elements no more than 0.05% each, 0.15% total
- Remainder aluminum (95.85–98.56%)
Annealed 6061 (6061-O temper) has maximum tensile strength no more than 150 MPa (22,000 psi), and maximum yield strength no more than 83 MPa (12,000 psi) or 110 MPa (16,000 psi). The material has elongation (stretch before ultimate failure) of 10–18%.
T6 temper 6061 has an ultimate tensile strength of at least 290 MPa (42,000 psi) and yield strength of at least 240 MPa (35,000 psi). More typical values are 310 MPa (45 ksi) and 270 MPa (39 ksi), respectively. In thicknesses of 6.35 mm (0.250 in) or less, it has elongation of 8% or more; in thicker sections, it has elongation of 10%. T651 temper has similar mechanical properties. The typical value for thermal conductivity for 6061-T6 at 25 °C (77 °F) is around 152 W/m K. A material data sheet  defines the fatigue limit under cyclic load as 97 MPa (14,000 psi) for 500,000,000 completely reversed cycles using a standard RR Moore test machine and specimen. Note that aluminum does not exhibit a well defined "knee" on its S-n graph, so there is some debate as to how many cycles equates to "infinite life". Also note the actual value of fatigue limit for an application can be dramatically affected by the conventional de-rating factors of loading, gradient, and surface finish.
6061 is commonly used for the following:
- construction of aircraft structures, such as wings and fuselages, more commonly in homebuilt aircraft than commercial or military aircraft. 2024 alloy is somewhat stronger, but 6061 is more easily worked and remains resistant to corrosion even when the surface is abraded, which is not the case for 2024, which is usually used with a thin Alclad coating for corrosion resistance.
- yacht construction, including small utility boats.
- automotive parts, such as the chassis of the Audi A8.
- some tactical flashlights
- aluminum cans for the packaging of food and beverages.
- SCUBA tanks (post 1995)
6061-T6 is used for:
- bicycle frames and components.
- many fly fishing reels.
- the Pioneer plaque was made of this alloy.
- the secondary chambers and baffle systems in firearm sound suppressors (primarily pistol suppressors for reduced weight and improved mechanical functionality), while the primary expansion chambers usually require 17-4PH or 303 stainless steel or titanium.
- The upper and lower receivers of many non mil-spec AR-15 rifle variants.
- Many aluminum docks and gangways are constructed with 6061-T6 extrusions, and welded into place.
- Material used in some ultra-high vacuum (UHV) chambers
- Many parts for remote controlled model aircraft, notably helicopter rotor components.
- Large amateur radio antennas.
6061 is highly weldable, for example using tungsten inert gas welding (TIG) or metal inert gas welding (MIG). Typically, after welding, the properties near the weld are those of 6061-T4, a loss of strength of around 40%. The material can be re-heat-treated to restore near -T6 temper for the whole piece. After welding, the material can naturally age and restore some of its strength as well. Most strength is recovered in the first few days to a few weeks. Nevertheless, the Aluminum Design Manual (Aluminum Association) recommends the design strength of the material adjacent to the weld to be taken as 165 MPa/24000 PSI without proper heat treatment after the welding. Typical filler material is 4043 or 5356.
6061 is an alloy that is suitable for hot forging. The billet is heated through an induction furnace and forged using a closed die process. This particular alloy is suitable for open die forgings. Automotive parts, ATV parts, and industrial parts are just some of the uses as a forging. Aluminum 6061 can be forged into flat or round bars, rings, blocks, discs and blanks, hollows, and spindles. 6061 can be forged into special and custom shapes.
6061 is not an alloy that is traditionally cast due to its low Silicon content affecting the fluidity in casting. Conversely, it can be suitably cast using a specialized centrifugal casting method. Centrifugally cast 6061 is ideal for larger rings and sleeve applications that exceed limitations of most wrought offerings. 6061 can be cast with many unique outer diameter characteristics.
Different forms and tempers of 6061 aluminum alloy are discussed in the following standards:
- ASTM B 209: Standard Specification for Aluminum and Aluminum-Alloy Sheet and Plate
- ASTM B 210: Standard Specification for Aluminum and Aluminum-Alloy Drawn Seamless Tubes
- ASTM B 211: Standard Specification for Aluminum and Aluminum-Alloy Bar, Rod, and Wire
- ASTM B 221: Standard Specification for Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes
- ASTM B 308: Standard Specification for Aluminum-Alloy 6061-T6 Standard Structural Profiles - According to ASTM, this was WITHDRAWN in 2019 with no replacement.
- ASTM B 483: Standard Specification for Aluminum and Aluminum-Alloy Drawn Tube and Pipe for General Purpose Applications
- ASTM B 547: Standard Specification for Aluminum and Aluminum-Alloy Formed and Arc-Welded Round Tube
- ISO 6361: Wrought Aluminum and Aluminum Alloy Sheets, Strips and Plates
- ASM Handbook, Volume 2: Properties and Selection: Nonferrous Alloys and Special-Purpose Materials ASM Handbook Committee, p 102 DOI: 10.1361/asmhba0001060[permanent dead link].
- Robert E. Sanders, Jr. (2001). "Technology Innovation in Aluminum Products". JOM. 53 (2): 21–25. Bibcode:2001JOM....53b..21S. doi:10.1007/s11837-001-0115-7.
- "Aluminum Alloys". Materials Management Inc. 23 December 2015. Retrieved 2016-07-25.
- Alcoa 6061 data sheet Archived 2006-10-20 at the Wayback Machine (pdf), accessed October 13, 2006
- Aluminum Standards and Data 2006 Metric SI, by the Aluminum Association Inc.
- ASTM B209
- ASTM B221
- Material Properties Data: 6061-T6 Aluminum
- ASM Material Data Sheet
- Aluminum Information at aircraftspruce.com, accessed October 13, 2006
- 6061 vs 2024 Archived 2013-01-25 at Archive.today. Homebuiltairplanes.com. Retrieved on 2012-04-04.
- Boatbuilding with Aluminum, Stephen F. Pollard, 1993, ISBN 0-07-050426-1
- EVOLUTION 9mm™, 1/2-28 TPI Archived 2011-08-01 at the Wayback Machine. Advanced Armament. Retrieved on 2012-04-04.
- Amphibian S .22LR : Suppressor : AWC Systems Technology. Awcsystech.com. Retrieved on 2012-04-04.
- "6061 Aluminum Alloy Forging | Anderson Shumaker". www.andersonshumaker.com. Retrieved 2015-10-08.
- "Aluminum Alloys | Johnson Centrifugal". johnsoncentrifugal.com. Retrieved 2019-10-14.
- 6061 (3.3214, H20, A96061) Aluminum. Retrieved on 2014-11-14.
-  ASTM B308
- "Properties of Wrought Aluminum and Aluminum Alloys: 6061 Alclad 6061", Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Vol 2, ASM Handbook, ASM International, 1990, p. 102-103.