Effect of deformation temperature and strain rate on dynamic recrystallized grain size of a powder metallurgical nickel-based superalloy

The high-temperature deformation behavior of a powder metallurgical nickel-based superalloy was investigated by compression tests under deformation temperature and strain rate ranges of 1110-1200 °C and of 0.01-10 s−1. Electron back-scatter diffraction (EBSD) technique was used to study the effect of deformation temperature and strain rate on the microstructure evolution and dynamically recrystallized grain size of this alloy during hot deformation. The experimental results indicate that the dynamically recrystallized grain size can be related to the flow stress through a power-law function. A new model is presented to investigate the relationship between the dynamically recrystallized grain size and the deformation temperature as to as the strain rate. The influence of temperature on the distribution of grain size are obvious different in different temperature range. The strain rate has a significant influence not only on average grain size, but also on the distribution of grain size. Dynamic recrystallization takes place in the interior of a number of grains when the deformation temperature at 1140 °C. The phenomenon of “the large grains absorb the small ones” will take place when the deformation temperature is increased to 1200 °C.