Temperature dependence of deformation mechanisms of a new Ni-based superalloy and high-temperature property optimization

Abstract

The influence of temperature on the deformation mechanisms of a new Ni-based superalloy named K4800 containing 35 vol% γ′ were investigated. We studied the temperature dependence of deformation mechanisms and used the alloying method to optimize the high-temperature properties of the alloy. By analyzing slightly deformed microstructures, the dominant deformation mechanisms of alloy K4800 at the yielding stage were identified as: the anti-phase boundary (APB) shearing from RT to 600 °C, stacking faults (SFs) shearing and Orowan looping at 600–800 °C, and Orowan looping/cross-slip/climbing above 800 °C. We found that it was the activation of thermally assisted processes declined the strengthening effect of γ′ phase and impaired the high-temperature strength of the alloy above 800 °C. First-principles calculations were employed to investigate the effects of alloying elements on the formation and stability of stacking faults in K4800 alloy by using a 48-atom Ni3(Al, Ti) orthorhombic supercell. Considering the effectiveness of elements in lowering stacking faults energy, Co and W elements were chosen to alleviate the strength degradation of K4800 alloy above 800 °C. The deformation mechanism and properties of these three alloys at elevated temperature were also revealed and discussed.