Through-Width and Through-Thickness Edge Effects on Tensile Properties of Thick AA2219 Plate

During the latter stages of the investigation into AA 2219 low, short transverse tensile ductility related to copper rich theta particles (Al2Cu), the NASA Engineering and Safety Center (NESC) team discovered an “edge effect,” where improved ductility and strength was observed in tensile specimens obtained from material close to the plate’s edges in the width direction. Therefore, an in-depth metallurgical investigation was carried out to determine the root causes of the edge effect. The investigation revealed a through-width edge effect and a through-thickness edge effect. With respect to mechanical properties, the edge effects manifested as variations in ductility and strength with respect to through-width and through-thickness locations. Thermo-mechanical processing of the material, specifically, rolling temperature, rolling strain, and quench rates, and their effects on microstructural evolution of theta particles are identified as root causes of the width and thickness edge effects. Additionally, differential scanning calorimetry was identified as an efficient and effective screening method for determining through-thickness areas of high Al-Cu eutectic phases which are associated with high concentrations of theta particles related to low ductility and strength.