6061-T6 Aluminium – The Ultimate Guide

  • Aluminium 6061-T6 is a sub-category of the 6061 alloy, one of the most widely used aluminium alloys..
  • The 6061-T6 alloy is used in applications where high strength to low weight ratios are critical such as the aircraft and aerospace industries.
  • It is the way the base Aluminium 6061 is treated that give Aluminium 6061-T6 it particular characteristics.
  • Compared to other Aluminium 6061 variations, 6061-T6 has better machinability characteristics, an improved anodizing response and comparable corrosion resistance properties.

Aluminium 6061-T6 is a subcategory of the 6061 aluminium alloy, one of the most widely used aluminium alloy categories in the world. The alloy is appreciated because of its versatile performance and all-around mechanical properties . The “T6” part of the 6061-T6 name indicates the type of the tempering treatment process that this aluminium alloy type undergoes.

6061-T6 aluminium parts being machined

Tempering treatment process

This treatment is a two step process, the first being the heating of the solution and the second the action of aging. During the first step, the alloy piece is submerged in a solution that has a steady temperature of 980 degrees F (527 degrees C). The piece stays in the solution for an hour before it is submerged in cold water. The first hour results in the dissolving of the alloying elements in the aluminium, while the quenching in the water achieves the mitigation of the precipitation of the individual alloying elements that would normally occur if the piece was left to cool gradually.

The next step is to age the piece, and this can be done via various methods all of which involve the raising of the temperature to about 350 degrees F (177 degrees C) for another 1-18 hours (exact duration depends on the shape, size, and type of application). If more designation digits and letters follow after T6, it means that the piece has been strain hardened (H1), strain hardened and annealed (H2), strain hardened and stabilized (H3), and finally strain hardened and painted or coated (H4).

Typically, and because the 6061-T6 alloy features the highest tensile strength of all 6061 types, it is used in applications where high strength to low weight ratios are critical. Examples include aircraft and aerospace applications, bicycle frames, fishing reel components, rifle components, vacuum chambers, and modelling products.

6061-T6 aluminium machined part

Aluminium 6061-T6 Properties and Data Tables

When compared to other 6061 alloy types that have been introduced to a different tempering procedure, the T6 boasts slightly better machinability characteristics as well as slightly improved anodizing response, but is also characterised by a lower level of formability. Its corrosion resistance properties, weldability, and brazeability remain pretty much the same as those of T1, T4, and O.

6061-T6 mechanical properties (rods, bars, tubes, pipes, and standard shapes)

Ultimate Tensile Strength38 ksi (262 MPa)
Max Yield Strength35 ksi (241 MPa)
Percentage of Elongation8% (at a thickness of less than 0.25″), 10% (for higher than 0.25″)
Elongation at Break12% (for a 1/16″ thickness), 17% (for a thickness of 1/2″).
Brinell Hardness95
Vickers Hardness107
Knoop Hardness120
Rockwell Hardness40 (scale A), 60 (scale B)
Ultimate Shearing Strength30 ksi (207 MPa)
Modulus of Elasticity10000 ksi (68.9 GPa)
Poisson’s Ratio0.33
Fatigue Strength96.5 MPa
Shear Modulus3770 ksi (26 GPa)
Shear Strength30000 ksi (207 MPa)

6061-T6 typical alloy composition

Aluminium97.2%
Magnesium1%
Silicon0.6%
Copper0.3%
Iron0.3%
Chromium0.2%
Zinc0.2%
Manganese0.1%
Titanium0.1%

6061-T6 physical properties and other useful data

Melting Onset1080 degrees F (580 degrees C)
Thermal Conductivity170  W/m-K
Thermal Expansion24 μm/m-K
Specific Heat Capacity900 J/kg-K
Electrical Conductivity43% IACS (equal volume), 140% (equal weight)
Calomel Potential-740 mV
Density2.7 g/cm3
Embodied Energy150 MJ/kg
Ultimate Resilience30 MJ/m3
Modulus of Resilience520 kJ/m3
Stiffness to Weight14 (axial), 50 (bending)
Strength to Weight31 (axial), 37 (bending)
Thermal Diffusivity68 m2/s
Thermal Shock Resistance14

About: Bill Toulas

Passionate engineer and new technologies advocate, writing about the ways they shape our world and amplify our very existence. Believes that engineering is the art of changing this world forever, everyday, little by little, and sometimes all at once.

No Responses to 6061-T6 Aluminium – The Ultimate Guide

  1. Andrew Masto says:

    Good rundown, but it should be mentioned that 6061-T6 is popular in many applications because it’s readily weldable using common processes such as GTAW (aka TIG) – whereas the stronger and more machinable alloys such as 7075 and 2024 are not. Both these stronger aluminum alloys are also a concern in regards to stress corrosion cracking, which limits their application. In contrast, 6061-T6 is considered to have good resistance to stress corrosion cracking.

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