Aluminum Precipitation Hardening
Multi-stage thermal treatment consisting of solution heat treatment, quenching, and aging, precipitating coherent nanoparticles within the aluminum lattice to significantly elevate the yield strength.
Precipitation hardening means: The material is first fully soft annealed so that everything dissolves cleanly. Then you let it age deliberately, either at room temperature or slightly warmed. Fine particles form in the structure, making the material really hard and strong. When welding, this is the classic: The heat from the weld destroys the condition in the heat-affected zone. The material becomes soft there again – that's called overaging. So if you've welded something, you have to re-solutionize and precipitation harden the whole zone afterwards, otherwise the spot stays soft and breaks under load. In practice, this means: After welding, put the whole part back in the furnace, fully solutionize, quench, and then artificially age. If that's not possible because the part is too big or you don't have a furnace, you have to design the weld so that it compensates for the missing strength – or the component is just less load-bearing at that spot.