ANALYSIS OF HOT DEFORMATION OF NIMONIC 80A USING PROCESSING MAP

The hot deformation behavior of NIMONIC 80A was studied in the temperature range of 900 - 1200 degrees C by employing the hot compression tests with the strain rates varying between 0.02 - 20 s(-1). The results showed that the strength during hot compression increased with increasing the strain rate and decreasing temperature. Hot deformation of NIMONIC 80A was well-described by the sinh creep law with the stress exponent of 4.4 and the activation energy of 424 kJ/mol. Processing maps were also constructed on the basis of a dynamic material model. At low strains, the processing map of NIMONIC 80A did not reveal any instability domain regardless of the strain rate and temperature. However, at high strains, the processing map exhibited an instability domain at low strain rates of 0.02 - 0.2 s(-1) and within a temperature range of 900 - 1000 degrees C. In the instability domain, no or partial recrystallization occurred and the deformed microstructure exhibited shear bands and carbide precipitation while full recrystallization occurred in the safe domain.