A compressive split-Hopkinson pressure bar and transmission electron microscope were used to investigate the mechanical behaviour and microstructural evolution of Inconel 718 at strain rates ranging from 1000 to 5000/s and temperatures between −150 and 550C. The results showed that the flow stress increased with an increasing strain rate or a reducing temperature. The strain rate effect was particularly pronounced at strain rates greater than 3000/s and a deformation temperature of −150C. A significant thermal softening effect occurred at between −150 and 25C. The microstructural observations revealed that the strengthening effect in deformed Inconel 718 alloy was a result primarily of dislocation multiplication. The dislocation density increased with increasing strain rate, but decreased with increasing temperature. By contrast, the dislocation cell size decreased with increasing strain rate, but increased with increasing temperature. It was shown that the correlation between the flow stress, the dislocation density and the dislocation cell size was well described by the Bailey–Hirsch constitutive equations.

Dynamic Mechanical Behaviour and Dislocation Substructure Evolution of Inconel 718 over Wide Temperature Range. W.S.Lee, C.F.Lin, T.H.Chen, H.W.Chen: Materials Science and Engineering A, 2011, 528[19-20], 6279-86