Nano-cutting mechanical properties and microstructure evolution mechanism of amorphous/single crystal alloy interface

PC Wang and JG Yu and QX Zhang, COMPUTATIONAL MATERIALS SCIENCE, 184, 109915 (2020).

DOI: 10.1016/j.commatsci.2020.109915

Amorphous alloys are widely used in metallic coatings because of their high strength and corrosion resistance. However, this coating material poses a challenge to its nano machining method, and the machining properties of the interface between amorphous alloys and single crystal alloys are rarely studied in depth. We used molecular dynamics simulation method to study the nano-cutting phenomenon and mechanism of Ni-Al metallic glass and single crystal composite. When only metallic glass was cut, we found that the high cutting velocity would lead to the instability in cutting metallic glass. The variation of cutting force was mainly determined by the transition of icosahedra and the size of the shear bands region. On the contrary, the slow cutting velocity gave shear bands enough time to generate and expand, which led to the stable cutting force when cutting metallic glass. The phase of single crystal was the most important part which affected the cutting stability when metallic glass and single crystal were processed at the same time. The fast cutting would break single crystal atoms into disordered atoms, making the cutting relatively smooth. However, the tool was in contact with both metallic glass atoms and single crystal atoms at a lower velocity when cutting the phase of single crystal, resulting in very unstable cutting. By comparing the surface roughness under different cutting velocities, we found that the lower the velocity was, the smoother the machined surface was. In addition, the interface from the metallic glass to the single crystal in the cutting direction could hinder the cutting to some extent, and the cutting force of the tool would increase to destroy the interface. However, the interface of the cutting direction from single crystal to metallic glass will not block the tool. When cutting velocities were not high, squeezed atoms would slide across the interface and the rest of the interface would not be damaged. This study is of great significance to strengthen the application of amorphous alloys.

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