6061 aluminium alloy
6061 is a precipitation hardening aluminium alloy, containing magnesium and silicon as its major alloying elements. Originally called "Alloy 61S" it was developed in 1935.[1] It has good mechanical properties and exhibits good weldability. It is one of the most common alloys of aluminium for general purpose use.
It is commonly available in pre-tempered grades such as 6061-O (solutionized) and tempered grades such as 6061-T6 (solutionized and artificially aged) and 6061-T651 (solutionized, stress-relieved stretched and artificially aged).
Basic properties
6061 has a density of 2.70 g/cm³ (0.0975 lb/in³).
Chemical composition
The alloy composition of 6061 is:
- Silicon minimum 0.4%, maximum 0.8% by weight
- Iron no minimum, maximum 0.7%
- Copper minimum 0.15%, maximum 0.40%
- 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 Aluminium (95.85%–98.56%)
Mechanical properties
The mechanical properties of 6061 depend greatly on the temper, or heat treatment, of the material. [2] Young's Modulus is 10x10^6 psi (69 GPa) irrespective of temper.[3]
6061-O
Annealed 6061 (6061-O temper) has maximum tensile strength no more than 18,000 psi (125 MPa), and maximum yield strength no more than 8,000 psi (55 MPa). The material has elongation (stretch before ultimate failure) of 25–30 %.
6061-T4
T4 temper 6061 has an ultimate tensile strength of at least 30,000 psi (207 MPa) and yield strength of at least 16,000 psi (110 MPa). It has elongation of 16%.
6061-T6
T6 temper 6061 has an ultimate tensile strength of at least 42,000 psi (300 MPa) and yield strength of at least 35,000 psi (241 MPa). More typical values are 45,000 psi (310 MPa) and 40,000 psi (275 MPa), respectively.[4] In thicknesses of 0.250 inch (6.35 mm) or less, it has elongation of 8% or more; in thicker sections, it has elongation of 10%. T651 temper has similar mechanical properties. The famous Pioneer plaque was made of this particular alloy. The typical value for thermal conductivity for 6061-T6 at 80°C is around 152 W/m K. A material data sheet [5] defines the fatigue limit under cyclic load as 14,000 psi (100 MPa) 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.
Uses
- 6061 is widely used for construction of aircraft structures, such as wings and fuselages, more commonly in homebuilt aircraft than commercial or military aircraft.[6] 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.[7]
- 6061 is used in automotive parts, such as wheel spacers.
- 6061 is used in the manufacture of aluminium cans for the packaging of foodstuffs and beverages.
- 6061 is used in SCUBA tanks (post 1995)
- 6061 was the material used for the Pioneer plaques.
- 6061-T6 is commonly used in the construction of bicycle frames and components.
- 6061-T6 is used in many fly fishing reels.
- 6061 T6 along with 7075 aluminium alloy is frequently used in the secondary chambers and baffle systems in firearm sound suppressors (primarily pistol suppressors for reduced weight and functionality), while the primary expansion chambers usually require 17-4PH or 303 stainless steel or titanium.[9][10]
Welding
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-O, a loss of strength of around 80%. The material can be re-heat-treated to restore -T4 or -T6 temper for the whole piece. After welding, the material can naturally age and restore some of its strength as well. Nevertheless, the Alcoa Structural Handbook recommends the design strength of the material adjacent to the weld to be taken as 11,000 psi without proper heat treatment after the weld. Typical filler material is 4043 or 5356.
Extrusions
6061 is an alloy used in the production of extrusions—long constant–cross-section structural shapes produced by pushing metal through a shaped die.
Forgings
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. Automotive parts, ATV parts, and industrial parts are just some of the uses as a forging.
References
- ^ 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.
- ^ Alcoa 6061 data sheet (pdf), accessed October 13, 2006
- ^ Aluminum Standards and Data 2006 Metric SI, by the Aluminum Association Inc.
- ^ Material Properties Data: 6061-T6 Aluminum
- ^ ASM Material Data Sheet
- ^ Aluminum Information at aircraftspruce.com, accessed October 13, 2006
- ^ 6061 vs 2024. 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. Advanced Armament. Retrieved on 2012-04-04.
- ^ Amphibian S .22LR : Suppressor : AWC Systems Technology. Awcsystech.com. Retrieved on 2012-04-04.