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6061-T6 Aluminium – The Ultimate Guide

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.

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.

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 Strength 38 ksi (262 MPa)
Max Yield Strength 35 ksi (241 MPa)
Percentage of Elongation 8% (at a thickness of less than 0.25″), 10% (for higher than 0.25″)
Elongation at Break 12% (for a 1/16″ thickness), 17% (for a thickness of 1/2″).
Brinell Hardness 95
Vickers Hardness 107
Knoop Hardness 120
Rockwell Hardness 40 (scale A), 60 (scale B)
Ultimate Shearing Strength 30 ksi (207 MPa)
Modulus of Elasticity 10000 ksi (68.9 GPa)
Poisson’s Ratio 0.33
Fatigue Strength 96.5 MPa
Shear Modulus 3770 ksi (26 GPa)
Shear Strength 30000 ksi (207 MPa)

6061-T6 typical alloy composition

Aluminium 97.2%
Magnesium 1%
Silicon 0.6%
Copper 0.3%
Iron 0.3%
Chromium 0.2%
Zinc 0.2%
Manganese 0.1%
Titanium 0.1%

6061-T6 physical properties and other useful data

Melting Onset 1080 degrees F (580 degrees C)
Thermal Conductivity 170  W/m-K
Thermal Expansion 24 μm/m-K
Specific Heat Capacity 900 J/kg-K
Electrical Conductivity 43% IACS (equal volume), 140% (equal weight)
Calomel Potential -740 mV
Density 2.7 g/cm3
Embodied Energy 150 MJ/kg
Ultimate Resilience 30 MJ/m3
Modulus of Resilience 520 kJ/m3
Stiffness to Weight 14 (axial), 50 (bending)
Strength to Weight 31 (axial), 37 (bending)
Thermal Diffusivity 68 m2/s
Thermal Shock Resistance 14