Zr₅₆Co₂₈Al₁₆ And Mg₆₅Cu₂₅Y ₁₀ A Comparative Study On The Mechanical Properties And Dynamic Behavior Of Bulk Metallic Glasses

As a kind of metastable material s,the amorphous alloy owns a more compact and disordered stacking state than the crystalline metal because of its"no defect"in microstructure,such as no dislocation,no grain boundary,no phase boundary,no segregation or inclusion.Therefore,bulk metallic glass?BMG?usually has good mechanical properties.However,the ductile and brittle bulk metallic glasses face with different application conditions,which is determined by the properties of the material itself.In this paper,ductile(Zr₅₆Co₂₈Al₁₆)and brittle(Mg₆₅Cu₂₅Y₁₀)bulk metallic glass and were studied,respectively.The mechanical,thermodynamic properties and crystallization kinetics of Zr-based and Mg-based amorphous alloy were analyzed by means of XRD,DSC,SEM combined with theoretical knowledge.At the same time,the compressive deformation behavior of Zr₅₆Co₂₈Al₁₆ under high temperature?supercooled liquid region?was studied,and further the effect of temperature on the deformation of amorphous alloy was discussed.Based on the microscopic images the deformation mechanism was determined.The special properties in the supercooled liquid region can be better used in the field of processing,which may be a theoretical guide for the practical application of bulk metallic glass.In the supercooled liq uid region,the rheological stress of amorphous alloy after thermal simulation decreases with the increase of temperature,but the rheological stress increases when the temperature reaches the crystallization temperature,which leads to the phenomenon of stress strengthening.SEM was employed to observe the fracture morphology of specimen after high temperature compression.The results showed that samples undergone other temperature didn't show the fracture except760K and displayed different morphologies of deformation.Both of Zr₅₆Co₂₈Al₁₆ and Mg₆₅Cu₂₅Y₁₀0 BMG samples experienced isothermal and non-isothermal annealing.The activation energies of two crystallization peaks of Zr₅₆Co₂₈Al₁₆ BMG obtained by non-isothermal heating based on OFW are332.3±34.44KJ/mol and 358.34±28.09 KJ/mol,respectively.Under the isothermal condition,Avrami exponent n for Zr₅₆Co₂₈Al₁₆ varies from 2.01 to 2.22,which the average value is calculated to be 2.1.However,the average activation energy for Mg₆₅Cu₂₅Y₁₀ BMG is 257.38KJ/mol.The nucleation rate of peak keep a nearly constant in the three dimensional controlled by diffusion.The activation energies of crystallization peak of Mg₆₅Cu₂₅Y₁₀ BMG obtained by non-isothermal heating based on OFW are 170.10±6.62KJ/mol.Under the isothermal condition,Avrami exponent n changes from 1.18 to 1.32,which the average value is calculated to be 1.28.The average activation energy is 86.85KJ/mol.The nucleation rate of crystal growing is almost zero in one dimension,resulting in interface crystallization.