Failure Behavior Of Copper-zirconium Metallic Glasses By Molecular Dynamics Simulations

Due to the particularity of their structure,metallic glasses(MGs)exhibit unique and excellent mechanical properties,have been widely used in various fields.In this paper,the molecular dynamics(MD)simulations are performed to systematically study the Cu-Zr binary MGs system,the deformation behavior and failure mechanism under different loading conditions are discussed,and the effects of different factors on the mechanical properties of MGs are compared.In this paper,the three-dimensional sizes of 28nm×56nm×5.6nm Cu-Zr MGs models are constructed using the large-scale atomic/molecular massively parallel simulator(LAMMPS).By setting different loading rates(10⁷ s^-1,10⁸ s^-1,10⁹ s^-1),adjusting different component concentrations(Cu₈₀Zr₂₀,Cu₆₄Zr₃₆,Cu₅₀Zr₅₀)and constructing different notch sizes(2nm,4nm,6nm,8nm)to simulate and study the microstructure changes of MGs under tensile loading,compressive loading,and cyclic loading.Combined with stress,potential energy,and deformation,the failure mechanism and mechanical behavior of MGs are analyzed.In the simulation under tensile loading and compressive loading,the normal tension stress on the shear surface promotes the formation of shear bands(SBs),however,the normal compressive stress is opposite,resulting in the compressive strength being slightly greater than the tensile strength.The higher loading rate will increase the density of SBs,expand plastic zone,and increase the yield strength;The increase of Cu percentage composition enlarges the elastic coefficient and increases the yield strength;The increase of notch depth accelerates the initiation and propagation of the SBs,expands the plastic deformation zone,and reduces the yield strength of the samples.In the fatigue test,the cycles to failure is mainly concentrated in the initiation stage of SBs,and the formation of SBs leads to structural damage,which is manifested as strain softening and energy storage capacity decline.The increase of Cu percentage composition shortens the cycles to failure,and the phenomenon of strain softening and energy storage capacity decline is more significant;The increase of the notch radian accelerates the aggregation of the shear transition zone(STZs),and the SBs are formed earlier,making the cycles to failure fewer.The research results in this paper provide a theoretical reference for explaining the deformation mechanism of MGs,which is helpful to further explore the mechanical properties of MGs and their composites.