Hot workability and models for flow stress of NIMONIC 115 Ni-base superalloy

The hot workability of the nickel-base alloy NIMONIC 115 has been investigated by means of torsion testing in extended ranges of strain rate (0.01–1 s−1) and temperature (1140–1180 °C). The flow curves have shown, in general, an increase in equivalent stress up to a peak value followed by a softening until rupture. At 1140 °C, for strain rates varying between 0.01 and 1 s−1, the peak in flow stress is followed by a marked softening up to a steady state condition which can be attributed to the occurrence of dynamic recrystallisation. The hot ductility vs. true temperature, occurring during torsion tests, has been analysed. Flow behaviour of NIMONIC 115 alloy vs. process parameters has been modelled by means of an equation relating the hyperbolic sine of flow stress to the temperature-modified strain rate. The results have been analysed and discussed.