Stress relaxation aging behavior and constitutive modelling of aa7150-t7751 under different temperatures, initial stress levels and pre-strains

Abstract

Age forming is an advanced manufacture technology for forming large aluminum paneTemperature, initial stress level and pre-strains have a great effect on the formability and performancThe stress relaxation aging behavior of AA7150-T7751 under different temperatures, initial strelevels and pre-strains was studied through stress relaxation tests, tensile tests and TEM observation.The results show that the formability can be improved with the increase of temperature, initistress levels and pre-strains. Deformation mechanisms during stress relaxation of the material weanalyzed on the basis of creep stress exponent and apparent activation energy. The aging precipitatof the studied alloy were not sensitive to the age forming conditions, but drastically coarsened over aging temperature, which decreased the mechanical properties. In addition, the relationshibetween stress relaxation behavior and aging strengthening is discussed. Based on the dislocatiotheory and the modified Arrhenius equation, a stress relaxation constitutive equation considering thinitial mobile dislocation density and temperature dependent activation energy was established. Thmodel can predict very well the stress relaxation behavior under various temperature, stress levand pre-strain conditions, with an average error of 2%.