When building a bike frame from scratch the the tubes, the machined or forged parts are all at a different temper and the welding creates another different temper. After the frame is welded it is annealed to attain the same temper throughout. Best practice would be do a post welding heat treatment process to restore the desired mechanical properties of the material back to how they were before the welding so you don't get a difference between the area of the weld and the rest of the tube. There is no reason why a after a repair has been made it couldn't be given a similar heat treatment.