The Research On Preparation Technology Of Zr-based Amorphous Alloy

This paper mainly studied the influences of the melt overheating treatment,cooling rate of the cooper mold and the added Nb elements on the glass-forming ability（GFA）, thermal stability, mechanical properties and mechanism of action of Zr-basedalloys.The alloys of Zr50.6Cu_27.6Al_9.2Ni_4.6Nb₈at different input powers （5kw,6kw,7kw）and different casting holding times （0.5min,1min,3min,5min）,Zr_51.7Cu_28.2Al-（9.4）Ni_4.7Nb₆and Zr_49.5Cu₂7Ni_4.5Al9Nb10of the step cut sample withdiameters of Ф3mm, Ф4mm and Ф6mm at the same input powers and casting holdingtimes,（Zr0.55Al0.10Ni0.05Cu0.30）100-xNbx（x=0,7,7.5,8,8.5,9） were prepared withcopper mold casting method. The phase composition, thermal stability, compressiontests and appearance of the strained sample of the alloys have been investigated by theX-ray diffraction （XRD）, differential scanning calorimeter （DSC）, universal testingmachine and scanning electron microscope （SEM）, respectively.The results show that, the casting temperature can increase the glass formingability and thermal stability of the BMG. With casting holding time increasing, theglass forming ability and thermal stability decreased under the same heatingtemperature and cooling rates. The compression fracture strength and compressiveplasticity were1955MPa and2.94%at the input powers of6kw and casting holdingtime of0.5min. There is an optimum casting temperature to the specific composition ofbulk amorphous alloy. Compression fracture strength and compressive plasticityincrease under the optimum casting temperature. Mechanical properties to someextents are controlled by casting temperature. The influence of cooling rate of thedifferent component samples on the glass forming ability and mechanical propertieswere investigated under the same casting conditions.The alloys of Zr_51.7Cu_28.2Al_9.4Ni_4.7Nb₆were pure amorphous structure with thediameter of3mm,4mm and6mm. The compression fracture strength and plastic strainof the diameter of3mm were1875MPa and1.36%, respectively. When the diameter is3mm, the compression fracture strength reached1921Mpa. The alloys ofZr_49.5Cu₂7Ni_4.5Al₉Nb₁0were pure amorphous structure while the diameter of3mm and4mm, but there were little crystal when the diameter of6mm. The compression fracturestrength of the diameter of3mm reached1803Mpa, the diameter of4mm1732MPa andits plastic strain reached1.52%. The effect of cooling rate on the glass-forming abilityand mechanical properties of amorphous alloys was significant. Compared with the large diameter amorphous alloy, the small size with the same chemical compositionshow more excellent plastic and good compression fracture strength.All of the (Zr_0.55Al_0.10Ni_0.05Cu_0.30)₁00-xNb_x（x=0,7,7.5,8,8.5,9） were pureamorphous structure. With Nb content increased, the glass transition temperature Tgand the crystallization temperature Tx first increased and then dropped, leading to thesame tendency of the supercooled-liquid-region ΔTx and parameter γ. The compressionfracture strength and compressive plasticity of (Zr_0.55Al_0.1Ni_0.05Cu0.3)_91.5Nb_8.5were1975Mpa and5.52%. There were a large number of shear bands at the side of fracture.The proper content of Nb increases the glass forming ability, thermal stabilitymechanical properties compression fracture strength and compressive plasticity ofZr-based metallic glasses.