Tensile deformation mechanisms at various temperatures in a new directionally solidified Ni-base superalloy

The effect of temperature on the tensile deformation mechanism in a new directionally solidified Ni-base superalloy, M4706, is investigated by transmission electron microscopy after yielding in the temperature range from room temperature to 1000 °C. It is found that below 750 °C, anti-phase boundary shearing and stacking fault shearing dominate the initial plastic deformation; above 900 °C, plastic deformation is accomplished predominantly by individual matrix dislocations bypassing γ′ precipitates, although a few isolated superlattice stacking faults are visible in the γ′ precipitates; whereas between these two temperatures, a transitional behavior is observed. Finally, based on the experimental observations, the variation of the formation of stacking faults with temperature and the relationship between the yield strength and the operative deformation mechanisms are discussed.