Superplastic deformation behavior of cold-rolled Inconel 718 alloy at high strain rates

Abstract

Cold-rolled Inconel 718 with a reduction of 84% exhibited excellent superplasticity at 950 °C with a high strain rate, which improves forming efficiency and reduces device dependency. The elongation to failure of 325% was obtained at a strain rate of 1 × 10−2 s−1. The ductility enhancement is attributed to the rapid atomic diffusion caused by dense dislocations and the grain refinement through recrystallization induced by cold rolling in the early deformation stage. Dislocation creep dominates the subsequent stretching process, accompanied by continuous dynamic recrystallization resulting from the transition of the accumulated dislocations into high-angle boundaries. The δ phase particles, which gradually coarsen and homogenize during deformation, promote recrystallization and hinder the dislocation motion. The cavities introduced by NbC particles primarily determine the material fracture. The present results provide a promising approach for developing superplastic superalloys adapted to high strain rates.