Sigmoidal creep of Ni3(Al, Ta)

Incremental creep tests have been used to explore the time-dependent plastic behavior of single-slip oriented Ni3(Al, Ta) at low temperatures in the anomalous flow regime. For selected incremental creep experiments at 20 and 100 °C, it was discovered that Ni3Al exhibited sigmoidal creep, where there is a significant time delay before the plastic strain rate accelerates to a maximum value during a creep experiment. Several of the factors that affect the sigmoidal creep response have been identified. The origin of sigmoidal creep is accounted for using a simple model of work hardening in Ni3Al, where the acceleration of the creep rate is a direct result of the annihilation of the existing dislocation substructure.