Thermal cycling creep behavior of NiAl–Cr alloy

Isothermal and thermal cycling creep behavior of a NiAl–Cr alloy was studied by compression tests. At low stresses, the thermal cycling creep rates were faster than the isothermal creep rates. The corresponding stress exponent under the thermal cycling condition was close to one. At high stresses, the stress exponent and the creep rate under the thermal cycling condition approached the isothermal values. The result indicates the occurrence of internal stress superplasticity at low stresses. The origin of internal stress was attributed to the difference in thermal expansion behavior of the constituent phases. Further, the thermal cycling creep rate was found to increase with increase in temperature amplitude and heating/cooling rate. The above trends were compared with the predictions of an internal stress superplasticity model. Good formability of the alloy under the thermal cycling condition was demonstrated through carrying out the thermal cycling compressive creep test to a large strain level.