Molecular dynamics study of nano-cutting mechanical properties and microstructural evolution behavior of Ni/Ni3Al phase structure

Ni/Ni3Al (gamma/gamma') phase interface structure in nickel-based single crystal alloys determines its excellent mechanical properties, which is widely used in aeroengine turbine blades. Because the deformation behavior of the gamma/gamma' phase interface under external force is very different from that of a single crystal without an interface, it is necessary to study the influence of the gamma/gamma' phase interface structure on nano-cutting performance. In this paper, molecular dynamics simulation is used to study the nano-cutting performance and mechanism of the gamma/gamma' phase interface structure. We found that the gamma/gamma' phase interface has a significant effect on the magnitude of cutting force and cutting stability. The cutting force of the gamma phase is greater than that of the gamma' phase, but the cutting stability is reversed. Surprisingly, the cutting force gradually decreases when the tool moves from they phase to the gamma' phase; and when the tool moves from the gamma' phase to the gamma phase, the cutting force gradually increases. When cutting processes are performed entirely in gamma phase and alternately in gamma and gamma' phases, respectively, nano-cutting deformation mechanisms are dominated by dislocation slip at lower speeds. The nano-cutting deformation mechanism transitions from dislocation slip to disordered atoms leading to unstable cutting forces when the cutting process is completely performed in the gamma phase at a cutting speed of 200 m/s. However, when the cutting process occurs alternately in the gamma and gamma' phases, the cutting deformation mechanisms of the gamma' and gamma phases are twins, point dislocations and stacking faults, respectively. Moreover, we found that the stacking defects of the gamma phase are absorbed by the gamma/gamma' interface when the tool moves from the gamma phase into the gamma' phase. But the dislocations are activated again when the tool moves from the gamma phase into the gamma' phase. Finally, we found that the surface roughness of the workpiece is the smallest at cutting speed of 100 m/s, which is manifested as pits and surface steps. This study will provide theoretical guidance for the nano-cutting scheme of nickel-based single crystal alloy. (C) 2022 The Author(s). Published by Elsevier B.V.