Why do heat treatments of aluminum alloys effect the proof stress more than the tensile strength?
Well doneBary H.You got my vote!I can only think that the fact of precipitation hardening brings the ultimate breaking stress to the limit of the crystal lattice can take.Pulling to destruction and precipitation hardening both generate dense locked dislocation fields.Now in the case of precipitation hardening this will be the case at the start of the test,the YPt will be close to the UTS,In the case of annealed material the YPt will start at a low-ish stress but the UTS(taking into account reduction in area of the fracture surface) may well be close to that of the aged material(bearing in mind that the aged alloy will not suffer much reduction in the area of the fracture surface.It’s very interesting,makes me wish i was still in the game to find out!
