Creep behavior of two-phase NiAl-9Mo eutectic alloy

The tensile creep behaviors of HIPed NiAl-9Mo eutectic alloy are investigated in the temperature range from 850 to 950 degreesC under the applied stress of 50-100 MPa. All the creep curves exhibit similar shapes: very short primary creep and long steady-state creep stages. The steady-state creep rate is found to depend on the applied stress and temperature. The power law stress exponent for steady state creep is determined to be 4.75+/-0.25 and apparent activation energy for creep to be 410.5+/-4.5 kJ/mol. The nucleation and propagation of creep cracks cause the beginning of the third creep stage. The creep fracture data can be described by the Monkman-Grant relationship. The alloy fails mainly by intergranular creep fracture and small partially by ductile fracture. The proportion of the former decreases as increasing stress at the same temperature.