Annealed 6061 (6061-O temper) has maximum ultimate tensile strength no more than 150 MPa (22 ksi), and maximum yield strength no more than 83 MPa (12 ksi) or 110 MPa (16 ksi). The material has elongation (stretch before ultimate failure) of 10–18%. To obtain the annealed condition, the alloy is typically heated at 415 °C for 2-3 hours.
T4 temper 6061 has an ultimate tensile strength of at least 180 MPa (26 ksi) or 210 MPa (30 ksi) and yield strength of at least 110 MPa (16 ksi). It has elongation of 10-16%.
T6 temper 6061 has been treated to provide the maximum precipitation hardening (and therefore maximum yield strength) for a 6061 aluminum alloy. It has an ultimate tensile strength of at least 290 MPa (42 ksi) and yield strength of at least 240 MPa (35 ksi). More typical values are 310 MPa (45 ksi) and 270 MPa (39 ksi), respectively. This can exceed the yield strength of certain types of stainless steel. 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 ksi) 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.