Study on constitutive relationships and processing maps for FGH96 alloy during two-pass hot deformation

The processing maps of FGH96 alloy with different strains have been investigated by isothermal interrupted hot compression test within the temperature range of 1050-1125 °C, the strain rate of 0.001-0.1 s−1, and the strain was 45+45%. The constitutive relationships which include the strain, strain rate and temperature were established and the microstructures of the first-pass and second-pass hot deformation were observed. The result showed that the dynamic recrystallization has occurred under different conditions. The first-pass hot deformation had a great influence on the flow stress of the second-pass. The curves of true stress-true strain between mathematical models and measured value were preferably fitted. The mathematical models could reflect the flow stress precisely under different conditions. Two instability zones of flow behavior were respectively established as follows: T=1080-1125 °C, ε′=0.01-0.1 s−1, ε<0.2 and T=1050-1125 °C, ε′=0.001 s−1, ε>1, which should be avoided during hot deformation. When power dissipation rate decreased as strain increased, the recrystallization grain coarsening happened. Otherwise, the recrystallization grain would be refined.