Yes, from my reference notes taken from the internet: (most 6061 you buy is T6)
ALUMINUM TEMPER DESIGNATIONS
Temper designations of wrought aluminum alloys consist of suffixes to the numeric alloy designations. For example, in 3003-Hl4, 3003 denotes the alloy and "Hl 4" denotes the temper, or degree of hardness. The temper designation also reveals the method by which the hardness was obtained. Temper designations differ between non heat-treatable alloys and heat-treatable alloys. and their meanings are given below:
Non Heat-Treatable Alloys
The letter "H" is always followed by 2 or 3 digits. The first digit indicates the particular method used to obtain the temper. as follows:
- H1 means strain hardened only.
- H2 means strain hardened, then partially annealed.
- H3 means strain hardened, then stabilized.
The temper is indicated by the second digit as follows:
2 1/4 hard
4 1/2 hard
6 3/4 hard
8 full hard
9 extra hard
Added digits indicate modification of standard practice.
Heat-Treatable Alloys
-F As fabricated
-O Annealed
-T Heat treated
The letter "T' is always followed oy one or more digits. These digits indicate the method used to produce the stable tempers, as follows:
-T3 Solution heat treated, then cold worked.
-T351 Solution heat treated, stress-relieved stretched, then cold worked.
-T36 Solution heat treated, then cold worked (controlled).
-T4 Solution heat treated, then naturally aged.
-T451 Solution heat treated, then stress relieved stretched.
-T5 Artificially aged only,
-T6 Solution heat treated, then artificially aged.
-T61 Solution heat treated (boiling water quench), then artificially aged.
-T651 Solution heat treated, stress-relieved stretched, then artificially aged (precipitation heat treatment).
-T652 Solution heat treated, stress relieved by compression. then artificially aged.
-T7 Solution heat treated, then stabilized.
-T8 Solution heat treated, cold worked, then artificially aged.
-T81 Solution heat treated, cold worked (controlled), then artificially aged.
-T851 Solution heat treated, cold worked, stress-relieved stretched, then artificially aged.
-T9 Solution heat treated, artificially aged, then cold worked.
-TlO Artificially aged, then cold worked.
Added digits indicate modification of standard practice.