Study on the Influence of Nickel Additions on AA7020 Formability Under Superplastic Forming Like Conditions

Abstract

This study set out to look at the influence of nickel additions on a commercially available AA7020 to understand the impact of the resultant intermetallics on recrystallization, formability and material strength. Elevated temperature tensile testing across a range of strain rates (5 × 10−4 s−1 × 10−1 s−1) and three temperatures (450− 500 °C) to compare material ductility followed by gas bulge testing at 475 °C and two gas pressures to investigate formability in a test closer to industrial forming conditions. Material strength was established using standard tensile testing, and EBSD used to understand the microstructural evolution of the materials. It was seen that the nickel additions increased ductility of the material across all test conditions, coupled with increasing the material strength. This was achieved due to the formation of nickel rich intermetallics which refine the microstructure during pre-heating through particle stimulated nucleation and subsequently improve strength through precipitation hardening in aging treatments.Graphic