Grain refinement and superplasticity of Inconel 718 processed by Multi-Pass High-Pressure sliding

Inconel 718 was successfully processed by multi-pass high-pressure sliding (MP-HPS) for production of ultrafine-grained structures in rods with upsized dimensions. An ultrafine-grained (UFG) structure with an average grain size of ~ 140 nm was developed through rotation of 45°. Tensile testing at 1073 K with an initial strain rate of 2x10-2 s−1 led to superplastic elongations more than 400%. A relation is established between hardness and elongation to failure so that it should be possible to predict the advent of superplasticity only from the hardness measurement.