The influence of crystallographic texture and slip system strength on deformation induced shape changes in AA 7050 thick plate

Abstract

The development of a multiscale modeling formulation to predict the mechanical response of AA 7050 thick plate is presented. Due to the heterogeneous processing conditions of this material, a significant gradient in both texture and macroscale hardness is observed through the thickness of the plate. These gradients create substantial variations in material state and properties, and have limited the widespread employment of AA 7050 thick plate in flight-critical airframe components. An elasto-viscoplastic finite element formulation was employed in modeling the mechanical response of a tensile specimen machined through the thickness of the plate material. The tensile specimen displayed measurable differences in the mechanical response along its gage length, where the cross-sectional shape of the specimen became non-circular at the quarter planes of the plate while it remained circular along the centerplane. In addition, the centerplane strained more than any other location along the gage length. The modeling framework employed in this work was able to capture various trends observed in the small strain aspects of this mechanical response, by combining descriptions of the texture and slip system strength distributions with a polycrystal based finite element formulation. With this multiscale modeling framework, the influence of crystallographic texture and slip system strength on the mechanical performance of the thick plate material was explored. It was found that a description of both the gradients in texture and slip system strength were ultimately necessary to predict the experimentally observed mechanical response. If these two aspects of material structure were varied independently, the mechanical performance was not well captured.