An improved process for grain refinement of large 2219 Al alloy rings and its influence on mechanical properties

Abstract

The large 2219 Al alloy rings used to connect propellant tank components of a satellite launch vehicle to each other are conventionally manufactured by radial-axial ring rolling at 460 °C with 50% deformation, but often suffer from coarse elongated grain and low ductility. An improved process (hot ring rolling at 460 °C with 30% deformation, then air cooling to 240 °C, followed by ring rolling at 240 °C with 20% deformation) was tested for ring manufacturing. The corresponding microstructure evolution and mechanical properties of the produced rings were studied. The results show that the improved process can successfully be applied to manufacture the large 2219 Al alloy rings without formation of macroscopic defects, resulting in a product with fine and uniform grains after heat treatment. The fracture mechanism of both rings was mainly intergranular fracture. With the resulting grain size refinement due to the improved process, more homogeneous slip occured and the crack propagation path became more tortuous during the tensile testing process. Thus, the elongation in all three orthogonal directions was greatly improved, and the axial elongation increased from 3.5% to 10.0%.