Serrated flow behavior of GH536 superalloy under different loading rates at room temperature

Serrated flow phenomenon has been widely observed among different metals due to the potential influence on their applications.Uniaxial tensile tests of nickel-based superalloy GH536 were carried out at loading rates of 0.06,0.60,3.60,and 36.00 mm·min^(-1)at room temperature,respectively.The tensile stress-strain curves demonstrate repetitive and discontinuous yielding behavior,namely serrated flow.It is observed that the stress-strain curves were dominated by type B serration,and original annealing twin boundaries(TBs)were distorted to various degrees under comparatively different lower tensile rates.In contrast,the TBs almost disappear,and the type B serrations become smoother and regular under the higher loading rates.This phenomenon can be attributed to the interactions between TBs and dislocations during tensile deformation.Coupled effects of the mobile and immobile dislocations illustrate the unsteady amplitude of serrations observed in stress-strain curves.Transmission electron microscope images of tested pieces reveal the interaction of dislocation and TB,with dislocation tangling around the TBs.