Thermal cycling creep behavior of NiAl-Cr alloy

Isothermal and thermal cycling creep behavior of a NiAl-Cr alloy was studie d by compression tests. Al low stresses, the thermal cycling creep rates we re faster than the isothermal creep rates. The corresponding stress exponen t under the thermal cycling condition was close to one. At high stresses, t he stress exponent and the creep rate under the thermal cycling condition a pproached the isothermal values. The result indicates the occurrence of int ernal stress superplasticity at low stresses. The origin of internal stress was attributed to the difference in thermal expansion behavior of the cons tituent phases. Further, the thermal cycling creep rate was found to increa se with increase in temperature amplitude and heating/cooling rate. The abo ve trends were compared with the predictions of an internal stress superpla sticity model. Good formability of the alloy under the thermal cycling cond ition was demonstrated though carrying out the thermal cycling compressive creep test to a large strain level. (C) 2001 Elsevier Science Ltd. All righ ts reserved.