Temperature dependence of deformation mechanisms and tensile strength of a new Ni-Fe-base superalloy

After a standard heat treatment, the influence of temperature on the tensile strength and corresponding deformation mechanisms of a new Ni-Fe-base superalloy with a low γ' volume fraction are investigated in the temperature region between room temperature and 800 °C. Experimental results show that the yield strength of the experimental alloy is temperature independent below 700 °C, whereas, above the temperature, its yield strength decreases dramatically with temperature. Analyses of micromechanisms controlling the deformation behavior reveal that plastic deformation is accomplished mainly by anti-phase boundary (APB)-coupled dislocations shearing through γ' precipitates below 700 °C, while, above the temperature, the primary deformation mechanism changes from APB shearing to stacking fault shearing and then to precipitate bypassing via Orowan looping together with cross-slip and local climb of dislocations. Based on the experimental results, it is deemed that the transition in the operative strengthening mechanism with temperature accounts for the variation of the yield strength of the experimental alloy with temperature.