Experimental studies and constitutive modelling of anelastic creep recovery during creep age forming

This paper presents a study of anelastic creep recovery during creep-ageing of an aluminium alloy AA7050-TAF. Uniaxial Creep-Ageing and Recovery Test (CART) was used to characterise the influence of anelastic creep strain on total creep deformation for determining the actual amount of springback in creep age forming (CAF) process. CART was performed on aluminium alloy AA7050-TAF at 174°C between the stress levels of 137.5 to 162.5 MPa. A constitutive model was developed for the prediction of the creep-ageing and recovery response of material in creep age forming. A 'back stress' variable was used to represent the net effect of the internal stresses of the material which causes anelastic creep recovery. Other microstructural variables were introduced to model complex micro-mechanisms and hardening effects including solid solution hardening, dislocation hardening, and age hardening. It has been found that the permanent strain after creep-ageing depends not only on total creep strain but also on anelastic strain. Simulation results from the constitutive model developed in this study show a good agreement with experimental data.