Deformation Mechanism Of Cu₅0Ag₅0 Phase-separated Amorphous And Its Composite

In this thesis,molecular dynamics simulation,using embedded atomic potential（EAM potential）,studied the structure and mechanical properties of Cu₅₀Ag₅₀ amorphous alloy under quasi-static compressive strain,and the relaxation properties of samples under dynamic alternating stress loading.And the evolution of atomic structure.The research content is of great significance for further understanding the deformation and relaxation mechanism of phase-separated amorphous systems.The study on the mechanical properties of Cu₅₀Ag₅₀ samples under compression shows that for samples with different crystal fractions,the greater the crystal content,the greater the yield strength of the sample,and for samples with crystal content over 50%,as the strain increases,the Strain strengthening occurs in the stress-strain curve.By analyzing the atomic configuration of the sample during the compression deformation process,it is found that for the sample with less crystal content,the strain first appears in the softer Ag-rich matrix region,and as the deformation increases,the strain expands uniformly in the Ag-rich region.In addition,for samples with high crystal content,strip-shaped immature shear bands will appear in the crystal area when the material begins to deform.As the deformation increases,the shear bands will nucleate and grow in different single crystals.The direction of propagation of the tangent bands is not the same.The shear bands from different directions in different single crystals will hinder each other’s propagation,so plastic hardening will occur.Combining the change of the stress-strain curve and the distribution of the shear area,it is found that the decrease in stress during material deformation is due to the propagation of newly generated shear bands in the crystal,which leads to stress release,while strain hardening is caused by multiple shear bands in different directions.Caused by interaction.The study of the deformation-induced crystallization and dissolution phenomena during the compression process reveals that the crystal structure transformation originates from the concentration of shear strain in the corresponding regionMechanical analysis of Cu₅₀Ag₅₀ amorphous and gold samples under dynamic loading found that the Cu₅₀Ag₅₀ amorphous alloy sample is a viscoelastic material,and there are liquid-like regions with loose atomic arrangement inside,and these regions will undergo inelastic deformation under the action of alternating stress.The flow in the liquid-like zone will consume energy and cause a phase difference between the stress and strain of the system,causing mechanical hysteresis,and the higher the temperature,the more obvious the mechanical hysteresis.Through the study of its dynamic relaxation process,it is found that at low temperature,the movement of Ag atoms is the main factor affecting the relaxation behavior of the system.For the three samples with different phase separation degrees,the atoms with larger displacements are always concentrated in the rich In the Ag region,during the low-temperature relaxation process,Ag atoms mainly participate in the local atomic rearrangement process.A sample with a longer relaxation time has a greater degree of phase separation,and a sample with a greater degree of phase separation is less likely to be hindered by Cu atoms in the movement of Ag atoms,so more Ag atoms will participate in the low-temperature relaxation process.Finally,the loss modulus of the system changes.At high temperatures,because the crystal structure will appear in the system when the temperature rises,the appearance of the crystal structure will sharply reduce the content of fast atoms in the system and affect the a relaxation process.Analyzing the atomic structure during the relaxation process,it is found that crystalline nuclei appear in the Cu-rich region at the beginning of loading,and the strain is mainly concentrated in the Ag-rich region,and the atoms in the Ag-rich region will adhere to the original Cu atomic nucleus length under stress.Large,after loading,the crystals of the sample are mainly composed of FCC and HCP structures interlaced,with only a small amount of BCC structure.When studying the evolution of atomic structure through Voronoi polyhedrons,it is found that the content of fast atoms in the system is inversely related to clusters<0 0 12 0>.The formation of crystals during the relaxation process will lead to an increase in the number of clusters<0 3 6 3>and<0 4 4 4>.