Yes and no, a 6061 T6 isn’t nearly as hard as a 7075 T6. Different major alloying element, same process. The “T” temper is just a process, but two different pieces of 7075 that go through the same process should be the same hardness. That’s for heat treatable alloys, there’s also materials that gain strength through some work hardening processes like 5052 (different subject almost). Don’t know if that really answers your question, but to say “I want the hardnest aluminum so I’ll choose T9” completely misses the fact that T9 is just a process. As I mentioned ive been doing this stuff for years, but that doesn’t make me an expert…I’m like guy that read a lot about racing cars, but never sat behind the wheel on a track. It’s part of my job to have a good understanding of the product, but I don’t make it.
Dan