Effect of pre-deformation on creep age forming of 2219 aluminum alloy: Experimental and constitutive modelling

Applying pre-deformation to high strength aluminum alloy has significant impacts on shape formation and mechanical properties of component in creep age forming process. The suitable degree of pre-deformation can not only improve forming efficiency, but also attain sound mechanical properties. This paper experimentally investigates the effects of pre-deformation on creep strain, mechanical properties and microstructures of AA2219. The results show that pre-deformation can prolong the duration of primary creep stage and considerably facilitate creep strain. Through mechanical property tests, it is found that pre-stretched AA2219 possesses a high-performance peak ageing strengthening region with little fluctuation during creep ageing of 7-13 h. Further examinations by TEM tests indicate that this is due to the fact that the morphology of precipitates in this region remains unchanged without remarkable coarsening. Based on microstructural evolution and ageing strengthening theory, a set of physically-based creep ageing constitutive model is proposed. The developed model takes into account the effect mechanism of pre-deformation and incorporates the coupled interactions of microstructure, yield strength and creep strain. A good agreement between predicted and experimental values is achieved, which verifies the accuracy of the developed model. Hence, it provides the theoretical basis for the prediction of shape and properties in creep age forming of large-scale panel component.