Microstructure Evolution and Processing Map of Superalloy GH720Li during Isothermal Compression

Abstract

sothermal compression tests for superalloy GH720Li were conducted to investigate the effect of hot deformation parameters on microstructure evolution. The changing characteristics of flow stress during hot deformation were also studied. The flow instability area was calculated based on Prasad Plastic Instability Criterion and the hot processing map was obtained. The results showed that dynamic recrystallization was the main softening mechanism of GH720Li alloy during hot deformation. The peak and steady stress decreased significantly with an increase of test temperature and a decrease of the strain rate. Finally, three unstable areas have been found from the processing map.

Characterization of Hot Deformation Behavior and Dislocation Structure Evolution of an Advanced Nickel-Based Superalloy

“…According to the models, the workpiece was regarded as an energy dissipative system, and the instantaneous power P was dissipated through temperature rising (G content) and microstructure evolution (J co-content). Therefore, the total absorbed power P can be determined as [12][13][14]:…”

“…The value of η varies with the deformation temperature and the strain rate, which reflects the power dissipation rate. Meanwhile, for distinguishing the flow instabilities domains, an instability criterion was proposed by Prasad as follows [14]:…”

“…Superimposing the instability map on the power dissipation map can generate a processing map. Based on superalloy hot working processes, the processing maps could aid design and control to optimize workability and to get the desired microstructure [14,15].…”