I am currently doing an experiment on 2xxx series AL. After solution treatment, the strength and hardness dropped. can i account it due to its micro-structure? (i explained it saying that due to the alloying elements being dissolved in the aluminum. Without the effects of the alloying elements, the aluminum is soft and ductile and does not have high strength.) More importantly, i artificially aged it at 150, 200 and 250 degrees celsius. theoretically, the hardness of the metals should be lowest at 150, and highest at 250. However, i got the highest hardness for the metal which Artificially hardened at 150 degrees celsius. Thus i am lost on how to explain this phenomena, can anyone guide me?