Study On Crystallization Kinetics And Small Punch Mechanical Properties Of ZrTiNiCuBe System High-entropy Metallic Glasses

High-entropy metallic glasses have both the compositional characteristics of high-entropy alloys and the long-range disordered structure of metallic glasses,showing excellent performance and broad application prospects.High-entropy metallic glasses,like traditional metallic glasses,are in a"meta-stable"state in thermodynamics,and will change to a stable crystalline state when heated,but the delayed diffusion effect makes it show different crystallization behavior from traditional metallic glasses;in addition,the excellent mechanical properties of high-entropy metallic glasses are closely related to their unique deformation behaviors.At present,most researches on the mechanical properties of metallic glasses focus on conventional tensile,compression,etc.There are very few studies on the mechanical properties of small punches suitable for small specimens.Therefore,studying the crystallization kinetics of high-entropy metallic glasses and the mechanical properties of small punches provides necessary parameters for in-depth understanding of the crystallization kinetics of high-entropy metallic glasses and the deformation behavior of small specimens,which is of great significance.Based on this,in this paper,the ZrTiNiCuBe series high-entropy metallic glasses was prepared by the copper mold suction casting method,and the crystallization kinetic behavior and mechanism were studied by two methods of continuous heating and isothermal heating;The small punch test technology was combined with finite element simulation.The mechanical properties of ZrTiNiCuBe series high-entropy metallic glasses were studied.The analysis of crystallization kinetics shows that the variable temperature crystallization of ZrTiNiCuBe system high-entropy metallic glasses is a multi-stage crystallization process,which has obvious kinetic effects on the heating rate.The activation energy of variable temperature crystallization calculated by Kissinger equation is greater than 200k J/mol,showing good thermal stability.Compared with traditional metallic glasses,ZrTiNiCuBe series high-entropy metallic glasses have higher activation energy of variable temperature crystallization,wider crystallization regions,smaller Trg andγparameters,indicating that it has better thermal stability,slower crystallization transition process and relatively low amorphous forming ability.The isothermal crystallization of ZrTiNiCuBe series high-entropy metallic glasses is a single crystallization process,and the relationship between the crystallization volume fraction and time is in the shape of"S",which is a typical nucleation growth and large-scale transformation.The activation energy of isothermal crystallization was calculated using the Arrhenius formula,and the activation energy decreased with the increase of Zr content and increased with the increase of Co content.The range of Avrami index n obtained by the JMA equation is 1.5≤n≤2.5,indicating that the isothermal crystallization is a diffusion-controlled growth process accompanied by a decrease in the nucleation rate.Under the conditions of the small punch test,the load-displacement curve of the ZrTiNiCuBe high-entropy amorphous alloy has only an elastic deformation stage,brittle fracture as a whole,and obvious pop-in behavior,which is closely related to the generation of shear bands.The fracture morphology of the sample presents a typical vein-like pattern,and high-density shear bands are distributed in the center of the sample surface.The tensile strength R_m（FEA）of Zr_xTi Ni Cu Be（x=1.5,2,2.5,3,3.5at.%）obtained by finite element simulation is between 998～3309MPa,and the elastic modulus E（FEA）is between43～62GPa.between.The tensile strength R_m（FEA）of Zr₂Ti Ni Cu Be_（1-x）Co_x（x=0.1,0.2,0.3,0.4at.%）is between 1736～3161MPa,and the modulus of elasticity E（FEA）is between48～60GPa.Compared with the uniaxial tensile test results of Vit1 and Vit4,the tensile strength R_m（FEA）is larger,and the elastic modulus E（FEA）has little difference.