Research On Nanometric Cutting Of Amorphous Alloys By Molecular Dynamics Simulation

Due to its unique microstructure of long-range disorder and short-range order, amorphous alloys exhibit excellent mechanical properties, and have broad application prospects. The application of materials cannot be separated from its processing method research. Cutting, as an efficient and high-precision molding method, will be a hot in amorphous alloys processing. Currently, the cutting research about amorphous alloys is less, and subject to the constraints of existing experimental conditions in time and space scales, the cutting mechanism and clear physical picture is still unknown. Molecular dynamics, a numerical simulation method which can study the atomic trajectory at the micro level, make the cutting mechanism research of amorphous alloy feasible.The shear deformation, cutting force and workpiece temperature of amorphous alloy Cu50Zr50 were studied. In the shear deformation analysis, two cutting stages were found, the material accumulation-release at the initial time and subsequent stable cutting process. These two processes were observed obviously from cutting force curve. For the temperature of workpiece, the maximum value can reach 800 K, little higher than its glass transition temperature, and the changes in the structure of workpiece was also further analyzed.The potential energy and volume, the atomic trajectories, the evolution of shear transformation zones were studied. The analysis of potential energy and volume about chip layer and workpiece layer confirmed the opinion that the yielding of amorphous alloys is a process of glass transition. Combined with the instantaneous-type map, the atomic trajectories was also analyzed. Using two-dimensional simulation for the cutting of amorphous alloy Cu50Zr50, the evolution process of shear transition region was observed. It was found that the shear transition zones first driven under stress, then occurs deformation in the form of rheology.The cutting of monopropellant amorphous copper was simulated and crystallization phenomenon occurred. Common neighbor analysis(CNA) was used to study the crystallization process in the cutting. The result found that the grains formed in the rake face and tip of the tool firstly, and then grew quickly under stress. When the grains grew to contact with each other, growth stops, merger occurred. Merger first occurred in a local, and then expanded along the grain boundaries. Finally, the merger was completed by discharging the free volume of grain boundaries out. This process was also analyzed using the relative displacement vector. The potential energy and volume was also studied. This simulation found that these values have a sudden decrease in the elevated process due to crystallization. For the shear strain analysis of the cutting, periodically shear bands in the chip was founded, and the free surface of chip is serrated. Finally, combined with the atomic structure diagram, its concluded that the deformation is carried out at the amorphous state.