Research Crystallization Behavior And Mechanical Properties Of Zr-based Bulk Metallic Glass

In recent years, the research for bulk metallic glass (BMG) has been the focus of attention in material science due to the superhigh strength of the materials. However, BMG exhibit poor plasticity at room temperature resulting in brittle fracture on macroscopic, which greatly limits their application in the field of engineering materials. In order to further elucidate the fracture mechanism and look for strengthening methods of BMG, this paper studied the selected ingredients Zr65Ni10Cu15Al10and Zr52.5Ni14.6Cu17.9Al10Ti5with large glass forming ability and a certain of plasticity. Zr-based amorphous rod samples with diameter of3mm were prepared by the vacuum arc smelting and casting of copper blow method. Thermal stability of the material were analyzed by differential scanning calorimetry (DSC). The microstructure and section morphology of Zr-based BMG were analyzed by means of X-ray diffraction (XRD) and scanning electron microscope (SEM). Mechanical properties of them were studied by compression mechanical properties test and hardness test. Zr-based BMG have been discussed under different temperatures of crystallization behavior and different cooling methods after annealing affect on the mechanical properties, microstructure and morphology. For the more, we explore the deformation fracture mechanism of Zr-based BMG.First of all, the two selected Zr-based BMGs were experimented with mechanical properties of conventional test. Their compressive stress-strain curves show that there are two parts of plastic deformation stages and appear "sawtooth" rheological phenomenon. Both of them show good capability of plastic deformation. The Zr-Ni-Cu-Al-Ti of BMG appears the phenomenon of strain softening, which associated with the change of the free volume in the shear zone. The two kinds of BMG compression section of the main direction of shear are not along the direction of theoretical maximum shear stress direction. Their section morphology appear the typical "dimple" or river vein patterns and droplet-like substance on the section microscopic morphology conform to the free volume and adiabatic warming theoretical model.Zr-Ni-Cu-Al-Ti amorphous alloy in high temperature short time after heat treatment was cooled in three different ways respectively:water cooling, air cooling and furnace cooling. It was observed the changes in microstructure and fracture surface of the material and studied their influence on mechanical properties. The research shows that different cooling methods with different cooling rates of the samples caused the different degree of crystallization of amorphous alloy significantly. The stress distribution internal of the amorphous alloy was affected directly, which affected the mechanical properties of BMG.