The effects of size and temperature on mechanical properties and deformation mechanisms of γ/γ′ nanowires: a molecular dynamics study

Nickel-based superalloys are widely deployed in high-pressure compressors and turbine rotors in various aeroengines. Developing advanced processing strategies is essential to boost the service performance of the alloy. In this work, molecular dynamics simulations based on the modified analytical embedded-atom method are performed to investigate the uniaxial tensile behaviors of γ/γ′ nanowires (NWs). The cross-sectional sizes of NWs range from 1.416 to 4.249 nm, and the simulation temperatures vary from 100 to 700 K. Cross-sectional size and temperature serve as key factors for surface activity, which in turn exerts a significant influence on the mechanical properties. The results obtained demonstrate that the mechanical properties increase exponentially with increasing cross-sectional size but decrease linearly with the rising temperature. Surface activity, including surface energy and surface thickness, acts as the driving force for dislocation or slip nucleation and is regulated by size and temperature. The critical size threshold for the transition of deformation mechanisms from crystal slip to twin formation is approximately 2.75 nm, as the size and temperature have a synergistic effect on the surface energy. The coupled effect of size, temperature, and surface, each of which imposes distinct regulatory roles, respectively, collectively governs the deformation behavior and mechanisms of NWs. In small NWs, deformation is primarily dominated by dislocation glide. By contrast, in larger NWs, plastic deformation is dominated by twin-mediated plasticity that impedes the dislocation movement and lattice glide. The study reveals the coupled size–temperature–surface effects on the deformation behaviors, which provides a theoretical foundation for the design of superalloys used in extreme environments.