Molecular dynamics study on mechanical performance and deformation mechanisms in nanotwinned NiCo-based alloys with nano-precipitates under high temperatures

The molecular dynamics simulations are performed to investigate the mechanical behaviors of nanotwinned NiCo-based alloys containing coherent L12 nano-precipitates at different temperatures, as well as the interactions between the dislocations and nano-precipitates within the nanotwins. The simulation results demonstrate that both the yield stress and flow stress in the nanotwinned NiCo-based alloys with nano-precipitates decrease as the temperature rises, which come from the fact that the higher temperatures lead to generating the more defects during yielding and the lower dislocation density during plastic deformation. Moreover, the coherent L12 phase exhibits excellent thermal stability, which enables to hinder dislocation motion at elevated temperatures through the wrapping and cutting mechanisms of dislocations. The synergistic effect of nanotwins and nano-precipitates results in the more significant strengthening behaviors in the nanotwinned NiCo-based alloys under high temperature. In addition, the high-temperature mechanical behaviors of nanotwinned NiCo-based alloys with nano-precipitates are sensitive to the size and volume fraction of microstructures. These findings could be helpful for designing the nanotwins and nano-precipitates to improve the high-temperature mechanical properties in NiCo-based alloys.