Tempering, that's the hardening term. duh

db, I've never felt the need to temper aluminum, or done it. But that technique was "explained" to me while the annealing was "demonstrated". I remember the two applications explained for different uses in building a canoe using aluminum tubes.
I've used annealing several times since so I could flatten a tube to replace a thward and not have it split. Such as shortening a thwart to move it back to make the gear area bigger in front of the stern position.