Mechanical behavior of thin sheets machined from AA7050-T7451 plate

Monolithic structures machined from thick aluminum plate are being employed with ever-increasing regularity in applications such as airframes. Understanding the 'thin sheet' performance of the thick plate material is crucial for design. Recent improvements in the processing of plate alloys, including AA7050, have made plasticity and ductile processes much more relevant to properties such as fracture toughness. In this work, a set of tensile experiments was conducted using specimens of various thicknesses (0.508 mm and 3.175 mm) machined from 7050-T7451 plate in various gauges (50.8 mm, 101.6 mm, and 203.2 mm). It was found that there was no appreciable specimen thickness-dependence in the deformation behavior up to necking; however, differences in ductility were observed. Anisotropies in strength (slight) and ductility (significant) were observed, as were orientation-dependent differences in deformation-induced specimen surface roughening. In general, specimens with axes in the rolling direction (RD) were more ductile than those in the transverse direction (TD) and appeared to deform uniformly up to the point of failure. In the 50.8 mm and 101.6 mm gauges, 'troughs' roughly aligned with the RD appeared at the onset of yielding in the TD specimens. These features seem to be linked with the underlying microstructure and indicate a general nonuniformity in the deformation when loaded in the TD.