The Research On Crystallization Kinetics And Mechanical Properties Of Cu-Zr-Al-Dy Bulk Metallic Glass

The crystallization kinetics, microstructure as well as mechanical properties is one of important issues for materials science is one of key research directions in amorphous materials and physics. Cu-based metallic glasses especially Cu-Zr-Al system, as the amorphous alloy material of extremely have engineering promising, have attracted extensive attention since its Large glass-forming ability, excellent mechanical properties and lower cost.(Cu0.47Zr0.45Al0.08)98Dy2amorphous alloy ribbons and Cu47Zr45Al8,(Cu0.47Zr0.45Al0.08)98Dy2as well as (Cu0.46Zr0.44Al0.08Dy0.02)100-xFex(x=1,3,5,7) amorphous alloy cylindrical rods have been prepared by copper mold casting method and melt spinning method. The non-isothermal crystallization kinetics, mechanical properties as well as the influence of addition of Fe elements on the microstructure, thermal stability and mechanical properties of (Cuo.47Zro.4sAlo.08)98Dy2amorphous alloy were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscope (SEM) and Transmission electron microscopy(TEM). Some of the main results are listed following:Under the condition of continuous heating, as the heating rate is increased, the values of Tg, Tx and Tp of (Cu0.47Zr0.45Al0.08)98Dy2amorphous alloy ribbons are shifted toward a higher temperature region, suggesting that the amorphous ribbons have obvious crystallization kinetics. The effective activation energies including Eg, Ex and Ep were calculated with Kissinger and Ozawa equations by means of DSC Scans, Eg=342.9and357.2kJ/mol,Ex=413.8and429.3kJ/mol as well as Ep=467.3and484.9kJ/mol. The results reveal that growth of the grains is more difficult than the nucleation because Ep is larger than Ex. The exponent n are5.6and1.3, shows that the crystallization processes for the amorphous alloys are polymorphic crystallization controlled by interface. The crystallization process is that Cu10Zr7would precipitate primarily, then AlZr2.The compressive strength and microhardness of Cu47Zr45Al8amorphous alloy were1684MPa and628.8HV respectively. Since the addition of Dy element that the compressive strength and microhardness of (Cu0.47Zr0.4sAl0.08)98Dy2amorphous alloy were higher than Cu47Zr45Al8amorphous alloy,1724MPa and636.8HV respectively. The Failure of (Cu0.47Zr0.4sAl0.08)98Dy2amorphous alloy is splicing damage. The flat fracture surface shows well-developed uniform distributional vein patterns. Also it can be noticed that local melting as evidenced by the formation of "liquid droplets" takes place during shear deformation.The appropriate Fe addition can enhance structure of the amorphous alloys. The structure of the bulk alloy is completely amorphous when the Fe content is x=1,3, apparent nanoscale phase separation occurs in the as-prepared alloys. With the increase of the content of Fe, Fe content of5%and7%, amorphous alloy are crystallized, and crystallization product is DyFe2, CuioZr7, FeZr3and Fe2Zr other intermetallic compound. Appropriate Fe addition can also enhance Strength and ductility of the amorphous alloys. With the increase of Fe content, compressive strength and plasticity show a decreasing trend after the first increases. When the Fe content is x=3the alloy possesses largest compression strength (1835MPa) and plastic deformation (0.5%). When the Fe content is x=1, there are many near-parallel vein patterns, grained and staggered localized, on the fracture. When the Fe content is x=3, the main vein patterns extend along fracture direction. And there are more grained and staggered localized near-parallel vein patterns on both sides of the main vein pattern.