Aluminum Thermo-Mechanical Treatment

This is not heat treatment in the true sense, but cold working through forming. The structure is changed, the material becomes harder and stronger, but also more brittle. When welding, you have to be careful: the heat breaks down this effect again, and you get softening or stresses that can lead to cracks. If you want to bring the component back to its original state afterwards, only proper annealing helps. And don't forget: too much deformation eventually makes the part brittle, and no post-treatment will help then.