Characterization of hot deformation behavior of a P/M nickel-base superalloy using processing map and activation energy

The hot deformation behavior of a nickel-base superalloy prepared by powder metallurgy (P/M) was investigated by using isothermal constant strain rate compressing tests conducted in deformation temperature from 1000 °C to 1100 °C and strain rate from 0.001 s−1 to 1 s−1. The true stress–true strain curves show that the alloy has higher strength at the temperature of 1000 °C. The processing maps for hot working were established based on the variations of efficiency of powder dissipation with deformation temperature and strain rate, interpreted using dynamic material model (DMM). The processing maps demonstrate that strain markedly affected the instability regions. The efficiencies of powder dissipation obtained in the strain range from 0.1 to 0.7 are essentially similar, which indicates that strain has a slight influence on it. The alloy exhibits a better workability in deformation temperature range from 1060 °C to 1100 °C and strain rate range from 1 × 10−1.5 s−1 to 1 × 10−0.5 s−1 owing to lower activation energy. Moreover, the fine recrystallized grain region can be identified on the basis of Zener–Hollomon parameter map at strain of 0.6.

Research highlights▶ Strain has significant influence on the instability regions. ▶ Activation energy is closely related to dislocation density. ▶ Strengthening phases γ′ promote activation energy. ▶ Dislocation density increases with the increasing of strain rate. ▶ The sensitivity of activation energy to temperature decreases with the increase of temperature.