High-strain rate superplasticity of Inconel 718 through grain refinement by high-pressure torsion

A Ni-based superalloy (Inconel 718) was successfully processed by high-pressure torsion (HPT) under a pressure up to 6 GPa at room temperature. The grain size after the HPT processing was reduced to ~100 nm. Tensile testing at 1073 K led to the advent of superplasticity with a maximum elongation of 1190% at a strain rate of 2×10−2 s−1 which is well in the range of high-strain-rate superplasticity. This superplastic flow was accompanied by a significant decrease in the flow stress.