Atomic Simulations Of Plastic Deformation Behavior Of Cu₅₀Zr₅₀ Metallic Glass

Metallic glasses?MGs?,namely amorphous,can exhibit excellent mechanicalproperties,high magnetism andcorrosion resistance.It is widely applied in the fields of electronics,aerospace,defense and energy.Unlike crystalline materials,MGs do not have defects such as grain,grain boundary,dislocation and stacking fault.As a result,they cannot restrict mature shear band?SB?motion and suffer from catastrophic failure.Therefore,improve the plasticity of MGs haveattracted tremendous attention.Due to the limitations of modern electronic and optical microscopy,systematic investigation of the deformation mechanisms of MG using experimentalmethods is still challenging.Molecular dynamics?MDs?simulation can directly present the experimental result by atomic structure geometry,thus it is possible to perform the detailed motion of atoms.Therefore MDs simulation plays an important role in the study of micro mechanism of materials.In present paper,MDs simulations are usedto investigate the mechanical properties of MGs.Themain results and conclusions are as follows:?1?The effects of sample thickness,crystalline phase,nanoporous and temperature on the mechanical properties of Cu₅₀Zr₅₀MGs under tensile loadingare investigated.The results indicate that the plastic deformation changes from initial homogeneous flow to a dominant SB propagation,and ultimately again to homogeneous plastic mode mediated by a patternof multiple SBs with increasing thickness.The plasticity of MGs can be enhanced by the introduction of crystalline phase.For MG-matrix composites,the superior tensile ductility and nearly perfect plastic flow behavior occur during plastic deformation.The results further indicate that the introduction of nanoporous leads to the decrease of the plasticity ofMGs,which is due to the larger pore density.The results also indicate that temperature has great influence on the mechanical properties of MGs,and the formation of the SBscan be suppressed with the increase of the temperature.?2?In addition,the coupling effects of sample thickness and aspect ratio on the mechanicalproperties under tensile loading arealso investigated.This work is divided into three sections:one focus on homogeneous plastic flow region,and one focus on catastrophic failure region,and another focus on critical region.It is found that in homogeneous plastic flow region,the MGsshow fine plasticity.In the catastrophic failure region,the Cu₅₀Zr₅₀ MG fails bynecking or dominant SBs slip.In critical region there exists a transition point,below which thecritical fracture value is rapidly decreased.When the thickness is above this transition point thecritical fracture value is gradually decrease.?3?Finally,we study that the effect of crystal phase structure and crystal-amorphous interface?CAI?on the SBs initiation and propagation behavior of Cu₅₀Zr₅₀MG-matrix composites with a pre-existing crack is also studied.It is found that the crystal diameter has almost no effect on the peak stress of MG-matrix composites,because the change of crystal diameter not only influences the SB initiation around the CAI but also affects the magnitude of the repulsive force between CAI and SB.Namely,CAI plays two roles of generating the immature SB and hindering its propagation.The results also indicate that SB propagation behavior showed stronger dependence on the CAI.Compared with monolithic MGs,the crystal layer changes SBs propagation path of matrix composite with laminar crystal.Additionally,we introduce the disorder degree?i.e.entropy?method to analyze the formation process of SBs.This study provides the mentality for improving the mechanical properties and optimal the relationship between plasticity and strength of Cu₅₀Zr₅₀ MG.