Through Thickness Microstructural Gradients in 7475 and 2022 Creep - Ageformed Bend Coupons

Abstract

In creep-ageforming a material experiences continuously variable bending stresses through its thickness, from tensile to compressive, which are maximum at the surfaces. This can potentially result in through thickness microstructural gradients, due to interactions between the bending stresses, creep, and precipitation occurring during ageing, that can alter a component’s performance. The aim of the work reported here was to develop an understanding of these effects in an industrial creep ageforming process. For this purpose two aerospace alloys, 7475 and 2022, were ageformed by Airbus UK using industrial scale ageforming tools. Their microstructures were analysed in detail by TEM, and SAXS, which revealed significant through thickness microstructural changes after forming.