Effects of sudden changes in strain rate on hot deformation behavior of Inconel 718

Hot compressive deformation tests are carried out on Inconel 718 to investigate the evolutions of microstructure and flow stress under constant and varying strain rate conditions. It is found that both microstructure and flow stress go through transient periods after the sudden changes of strain rate. During the transient periods, the fraction of recrystallization and the flow stress gradually evolve toward to the values obtained at the corre-sponding constant strain rate. However, the durations of transient period in recrystallization and flow stress are different. After the sudden increase of strain rate, the durations of transients in flow stress and local misorien-tation are equal and are larger than that in the fraction of recrystallization. This indicates that the local misorientation can more comprehensively represent the transient microstructure state than the fraction of recrystallization. After the sudden decrease of strain rate, the transient period in flow stress is shorter than that in the fraction of recrystallization. The results also experimentally verify the pseudo-metadynamic recrystallization, a phenomenon previously found from simulation results.

Automated summary

Hot compressive deformation tests were conducted on Inconel 718 to study the evolution of microstructure and flow stress under constant and varying strain rate conditions. It was observed that after sudden changes in strain rate, both microstructure and flow stress exhibited transient periods. The fraction of recrystallization and flow stress gradually evolved towards values obtained under the corresponding constant strain rate. The durations of the transient periods were found to be different for recrystallization, flow stress, and local misorientation, with local misorientation being a more comprehensive indicator of the transient microstructure state.