Study on superplastic behaviour of cold rolled Inconel 718 alloy with δ phase dispersion distribution

ABSTRACT Cold-rolled Inconel 718 with δ phase dispersion distribution was prepared and exhibited excellent superplasticity at 950°C with a strain rate of 6 × 10−4 ~4 × 10−3 s−1. The elongation to failure of 561% was obtained at a strain rate of 1 × 10−3 s−1. Superplastic deformation accelerates the recrystallization of cold-rolled deformed microstructure, thus improving grain uniformity. The dispersed δ phase promotes the nucleation of recrystallized grains and pin grain boundaries to limit grain size. Diffusion-coordinated grain boundary slip is the main deformation mechanism of the alloy sheet during superplastic stretching. The dense dislocations in the deformed grains act as the channel of atomic diffusion in the early deformation stage. Subsequently, the material conversion between grain boundaries promotes atomic diffusion. The present results have certain reference significance for preparing and forming superplastic Inconel 718 alloy.