Effect Of Co Substitution On Mechanical Properties And Crystallization Behavior Of ZrCuAlNi Bulk Amorphous

In this paper,Zr_55.7Al_11.3Ni_5-xCu₂₈Co_x?x=0,1,2,3,4,5at.%?.With a diameter of2-8mm was successfully prepared using a combination of non-consumable arc furnace melting and copper mold casting.)bulk amorphous alloy.X-ray diffractometer?XRD?,scanning electron microscope?SEM?,differential scanning calorimeter?DSC?,energy spectrometer?EDS?,and Instron universal material testing machine were used to analyze the analysis of Co element replacing Ni element Effects on the GFA,thermal stability,crystallization behavior and mechanical properties of Zr_55.7Al_11.3Ni_5-xCu₂₈Co_x alloy system.XRD and DSC test results show that with the increase of the amount of Co added,the amorphous forming ability of the alloy gradually increases,and then weakens.When the content of Co is 2at%,the reduced glass transition temperature Trg reaches a maximum value of 0.6147,and the corresponding maximum critical dimension is 8mm.This is because the addition of Co increases the degree of chaos in the alloy system,increases the system's positional entropy,causes the rearrangement of atoms in the cooling process of the alloy,and hinders nucleation.The mechanical property tests show that the compressive fracture strength gradually increases to the maximum strength and then decreases rapidly with increasing Co content.The compressive fracture strength reached a maximum value of 1940 MPa at a Co content of 2 at%,and the corresponding maximum compressive strain was 7.41%.It can be seen that the addition of Co element has an important influence on the mechanical properties of the amorphous alloy of the system.Adding an appropriate amount of Co element can obtain good mechanical properties.The DSC test method was used to study the thermodynamic behavior at five different heating rates.The curves show that the characteristic temperatures are shifted to the high temperature region,indicating that the glass transition and crystallization process conform to the kinetic law.The maximum width of the subcooled liquid region with Co added is 61K At the same time,the Kissinger equation was used to calculate the activation energy of amorphous crystallization.The Co content of Ex and Ep was 2at%.The values were 316.4?KJ/mol?and 320.5?KJ/mol?.The reason may be that the addition of Co forms tighter short-range atom clusters,which hinders the migration and diffusion of atoms in the glass transition and crystallization processes.The amorphous ability and the thermal stability of the alloy tend to increase and then decrease.Zr_55.7Al_11.3Ni₃Cu₂₈Co₂ system amorphous alloy was selected,and five pre-annealing tests were performed respectively.The morphology and elemental analysis of precipitated phases were analyzed by SEM and EDS analysis methods.The change of free volume and crystallinity during the annealing process,through the change of the annealing structure,explore and analyze the fracture mechanism of the alloy,the effect of the annihilation of free volume and the structural change on the properties of the alloy.