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

Key words: 
• NiCo-based alloys /
• high temperature /
• nano-precipitate /
• nanotwins /
• molecular dynamics simulation /
• mechanical behavior /
• deformation mechanism /
• dislocations

Abstract: Molecular dynamics simulations are performed to investigate the mechanical behavior of nanotwinned NiCo-based alloys containing coherent L1$_{2}$ 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, because the higher temperatures lead to the generation of more defects during yielding and lower dislocation density during plastic deformation. Moreover, the coherent L1$_{2}$ phase exhibits excellent thermal stability, which enables the hinderance of dislocation motion at elevated temperatures via the wrapping and cutting mechanisms of dislocations. The synergistic effect of nanotwins and nano-precipitates results in more significant strengthening behavior in the nanotwinned NiCo-based alloys under high temperatures. In addition, the high-temperature mechanical behavior of nanotwinned NiCo-based alloys with nano-precipitates is sensitive to the size and volume fraction of the microstructures. These findings could be helpful for the design of nanotwins and nano-precipitates to improve the high-temperature mechanical properties of NiCo-based alloys.