Temperature dependence of deformation mechanisms of a new Ni-based superalloy and high-temperature property optimization
Pengfei Zhao, Heyu Zhu, Kunlei Hou, Min Wang, Xianchao Hao, Weiwei Xing, Ming Gao, Xing‐Qiu Chen, Yingche Ma
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.