Study On Nanomechanical Properties And Nanocutting Mechanism Of Amorphous Alloy

With the development of technology, there are great demands from different industries for material properties and machinability of products. To achieve a wide use of materials with good quality, researchers have conducted studies to explore material properties and processes.Amorphous alloy, also called metallic glass, is a new kind of material with the short-range disorder and long-range order. Because of the amorphous structure, it has a good mechanical strength, toughness, magnetism, corrosion resistance and friction resistance. It has been widely used in areas such as machinery, aviation, aerospace and micro-electronics. However, less understanding of mechanical properties and machinability of materials has limite the applications. Cu₅₀Zr₅₀ is a kind of classic binary amorphous alloy and can well reveal characteristics of amorphous alloy.Since it is difficult to directly observe the deformation processes of amorphous alloy by in-situ experiments with atomic-scale resolution, molecular dynamics?MD? provides a powerful approach to gain deeper understanding to the deformation mechanism of amorphous alloy from the nanoscale. It has been an effective way to study nanomechanical and nanocutting properties of materials. Nanoindentation and nanocutting molecular dynamics simulations are conducted respectively to the nanoindentation model and nanocutting model of Cu₅₀Zr₅₀ amorphous alloy in the paper. For the nanoindentation of Cu₅₀Zr₅₀ amorphous alloy, such aspects are studied as the material deformation behavior, the force, mechanical property parameters of the material, the local temperature, formation and development of “shear transformation zones?STZs?” during the nanoindentation process and the effect of different indentation parameters on the process of Cu₅₀Zr₅₀ amorphous alloy. The results show that: “STZs”?inhomogeneous plastic deformation of amorphous alloy? constantly migrate and grow during the indentation process. The temperature in the contact zone between indenter and substrate is the highest. When the temperature rises to 85% of glass-transition temperature of the material, free volume would decreases to a certain degree, substrate atoms would be random-close-packed and the motion of atoms would be close to stagnation, which causes fluctuation of material properties. The indentation parameters have great effects on the deformation behaviors of Cu₅₀Zr₅₀. A higher loading speed causes the increase of material's hardness and elastic modulus, while the material's hardness and elastic modulus decrease with an increase in temperature. Compared to the virtual indenter simulation, in the simulation of a diamond indenter, obvious adhesion can be seen from the loading curve and unloading curve.For the nanocutting of Cu₅₀Zr₅₀ amorphous alloy, such aspects are studied as the material deformation, formation and development of “STZs”, the temperature and the effect of different cutting parameters on the process of Cu₅₀Zr₅₀ amorphous alloy. The results show that: During the nanocutting process of Cu₅₀Zr₅₀ amorphous alloy, material removal is mainly under the effect of the extrusion. The formation of “STZs”?inhomogeneous plastic deformation of amorphous alloy? in the cutting region can be clearly observed in the workpiece. The plastic deformation of amorphous alloy is affected by “STZs”. The simulation parameters have great effects on the nanocutting behavior of Cu₅₀Zr₅₀. The cutting depth and cutting speed have significant effect on the temperature distribution of the workpiece and average Newtonian layer temperature of the tool. When the cutting regional temperature has surpassed the glass-transition temperature of amorphous alloy, glass-transition of the material would happen in high-temperature regions, which strengthens the plastic flow of the material, thus making the material removal better proceed in the way of plasticity.