AL 6061-T6 vs AL 6061-T651 Sheet and plate

[CheckerRon]

This question was posted Jan 2005 with mixed and indefinite results, so I am asking again.

Is the difference strictly thickness cutoff i.e.> .5" (13mm) or is it the solution heat treat and stretching process that defines which is which?

I am not asking about T6511, since it is (I believe) tube or extruded shapes.

 

[TVP]

It is both. ASTM B 209/B 209M shows that 6061-T6 is only available below 6.30 mm, with 6061-T651 only available in thicknesses larger than 6.30 mm. The manner in which the T651 temper differs from the T6 temper is that T651 requires a stretching process (1.5-5% permanent strain) after solution heating, with no subsequent straightening after stretching. T651 only applies to plate (thicknesses > 6.3 mm), to rolled or cold-finished rod & bar, and forgings and rings.

 

[CheckerRon]

Thanks TVP. Did not have ASTM B209 handy.