Molecular Dynamics Study Of Femtosecond Laser Ablating CuZr Amorphous Alloy

The amorphous alloy with outstanding physical-chemical properties and widely application prospects is becoming a hotspot in the field of materials science research in recent years. However, The excellent physical and chemical and mechanical performance of amorphous alloys will change with the structural relaxation and crystallization because of their unstable structure. These unique properties will disappear immediately when the crystallization occurs during the processing. Based on the survey of the relevant literature, the amorphous alloy processing without crystallization can achieve using the appropriate femtosecond laser.This paper simulates the ultra-short pulse laser interaction with Cu Zr amorphous alloy with the Molecular Dynamics combined the Two-Temperature- Model. The work studies the mechanism of relaxation time, target removed,and heat transport. It has an important role for the wide application of femtosecond laser micro-processing and amorphous alloy. It also provides a possible model and the theoretical basis for related research. The main work and conclusions as follows:(1) On the basis of investigation of the relevant literature,I have understood the background research project and Significance of this topic;I have summarized the progress of femtosecond laser processing technology and theoretical model of femtosecond laser interaction with metal; I have expounded the molecular dynamics method and its solution process in detail, I have summarized the parameters and initial conditions and boundary conditions in this model.(2) This paper selects the appropriate potential function to study the interaction of femtosecond laser and amorphous alloys. On this basis, we use Lammps software to simulate and then test and verify, we use the VMD and MATLAB to analysis data.(3) I analysis the thermal relaxation process and mechanism of heat transfer of femtosecond laser irradiation. We find that under femtosecond laser irradiation, Cu Zr amorphous alloy is heated slower than crystalline mental like Cu and Ni. Caused by the thermal expansion and stress wave, the film will appear periodically expansion-contraction. We conclude heat transport mechanism as follows: First, almost all of the free electrons absorb energy and their temperature rise rapidly. Then, the heat quickly spread because of electronic thermal conductivity, but due to the interaction between electrons and atoms, atomic temperature gradually increased, while the atomic temperature is also affected by the material heat shock wave.(4) We have analyzed the material ablation mechanism with different laser fluence. The gas bubbles generate inside the target when the absorbed fluence is regulated from 30 m J/cm2 to 45 m J/cm2,resulting in varying degrees of structural damage film, fracture and decomposition. The average size and the number of the gas bubbles are strongly dependent on the laser fluence.