Solution Annealing
High-temperature heat treatment designed to dissolve second-phase precipitates back into solid solution, followed by rapid quenching.
In solution annealing, you heat the material completely so that unwanted precipitates dissolve back into the base material. Then you quench it quickly so that the dissolved components don't precipitate again and the structure stays clean. If you mess this up – cooling too slowly or not holding the temperature – you get a coarse grain and the weld becomes brittle. You'll notice it at the latest during machining or when the part breaks. Make sure the component is really heated through, otherwise you only dissolve superficially. And the cooling must be quick and uniform across the whole cross-section, then it'll be fine.