Effect Of Crystallization Behavior On The Mechanical Properties Of Copper-Zirconium Metallic Glasses

Metallic glasses（MGs）have received a lot of attention because of their unique disordered structure,excellent properties and promising applications.Due to being in a thermodynamically sub-stable state,MGs undergo a spontaneous transition to the corresponding crystalline phase under certain conditions,i.e.,crystallization behavior.This article uses molecular dynamics（MD）simulation software LAMMPS to construct a copper-zirconium MG model and simulate its loading deformation process,the model size is（24.7nm×49.4nm×6.2nm）.The effects of different cooling rates,different annealing temperatures and different annealing times are discussed in the melt cooling and isothermal annealing processes of MGs,respectively,and the microstructure of the system under different conditions is characterised.The stresses,strains,LS（large-strain）atomic occupancies and strain localisation parameters of the systems under different conditions are output under applied loads,and the deformation processes and mechanical properties of the different models are analysed in comparison with the shear band（SB）deformation mechanism.The main contents of this article include:（1）Compression simulations are conducted at room temperature on metallic glasses and partially crystallized metallic glasses obtained at four different cooling rates(5×10¹¹K/s,1×10¹²K/s,5×10¹²K/s,1×10¹³K/s),and the effect of different cooling rates on the mechanical properties of metallic glasses is analyzed.The higher cooling rates result in lower yield strength,better plasticity and a gradual change in the deformation mode from localised to non-localised deformation;the softening of partially crystallised MGs is reduced,the yield strength is substantially increased and the SB dominates the plastic deformation.（2）The glass transition temperature of Zr₈₅Cu₁₅MGs is determined and different annealing temperatures（500K to 1400K）are chosen depending on the glass transition temperature.Different annealing temperatures change the internal microstructure of MGs and consequently affect their mechanical properties.MGs are most sensitive to annealing near the glass transition temperature,and excessive crystal phase volume fractions cause MGs to exhibit a high degree of localised deformation.（3）MGs are treated with different annealing times（150ps to 1200ps）,and the effect of annealing time on the mechanical properties of MGs is given by analysing the simulation results of compression and tension of MGs.The volume fraction of the crystalline phase within the MG increases with increasing annealing time,but the dimensional change is not significant;the yield strength of the annealed MG is slightly lower under tensile loading;with increasing annealing time,the plastic deformation is concentrated within a single SB and the localised deformation is more pronounced.This article summarizes the influence of crystallization behavior under different conditions on the mechanical properties of metallic glasses,providing some reference for the application of metallic glasses in complex environments.