Research On The Ablation Mechanism Of Metallic Glass Processed By Femtosecond Laser

Metallic glasses are one of the hot materials currently under study because of their excellent mechanical,chemical and physical properties.However,metallic glasses are sub-stable,and conventional processing methods are prone to high temperatures or high stresses that lead to crystallization,and the corresponding excellent properties are changed.Among the metallic glass processing methods,femtosecond laser processing is unique because of its small heat-affected area,high precision,and non-contact processing.It can solve the problem of atomic structure transformation in metallic glass processing,and can also realize the manufacture of complex metallic glass structure.However,there are extreme phenomena such as short pulse duration and physical problems involving multiple scales in femtosecond laser processing of metallic glasses,which greatly increase the difficulty for understanding the relevant ablation mechanisms.Compared with the complex equipment conditions required experimentally,the simulation method can be used to study the femtosecond laser processing of metallic glass more intuitively,thus contributing to further understanding of the ablation mechanism of femtosecond laser processing.In the femtosecond laser processing of metallic glass,parameters such as pulse duration and absorbed fluence have different effects on the ablation results.In order to investigate the effects of these parameters on the ablation results,this paper uses a two-temperature model combined with molecular dynamics to study Cu₅₀Zr₅₀metallic glass with a thickness of 645 nm.（1）The effect of absorbed fluence on single-pulse femtosecond laser processing of Cu₅₀Zr₅₀metallic glass was investigated.The effects of the absorbed fluence on the lattice temperature,pressure and number density of Cu₅₀Zr₅₀metallic glass were investigated at 100 fs pulse duration and 90 m J/cm²,100 m J/cm²,160 m J/cm²,and 200m J/cm²absorbed fluences,respectively.The results show that with the increase of absorbed fluence,the lattice temperature and pressure of the material are higher.（2）The effect of pulse duration on single-pulse femtosecond laser processing of Cu₅₀Zr₅₀metallic glass was investigated.The effects on the electron-lattice temperature coupling time and maximum electron temperature of Cu₅₀Zr₅₀metallic glass were analyzed at 50 fs,100 fs,200 fs,and 500 fs pulse duration with 160 m J/cm²absorbed fluence,respectively.The internal stress and number density variations of the femtosecond laser-induced target were also analyzed.The results show that with the increase of the laser pulse duration,there is no significant difference in the electron-lattice coupling time and equilibrium temperature when the electron temperature and lattice temperature reach equilibrium.（3）The effect of delays on double-pulse femtosecond laser processing of Cu₅₀Zr₅₀metallic glass was investigated.Based on the single-pulse femtosecond laser ablation study,the effects of 5 ps,10 ps,50 ps,and 100 ps delays on the electron-lattice temperature evolution and atomic structure changes of the double-pulse femtosecond laser processing of metallic glass were analyzed.The internal stress and number density changes induced by the double-pulse femtosecond laser on the target were also analyzed.The results show that the removal of the target material is mainly caused by the formation and expansion of double voids when the pulse delay were 5 ps,10 ps,and 50 ps.And the removal of the target material is mainly caused by the expansion of single void when the pulse delay time is 100 ps.