Study On The Alloying Element Ti Influence On ZrCu Based Bulk Amorphous Alloy In Amorphous Formation Ability And Performace

The research about the improvement of the glass-forming capabilities and theperformance can promote the development and application of amorphous alloys.Based on the existing amorphous alloy Cu₄₆Zr₄₆Al₈, we have prepared new bulkamorphous alloys Cu₄₆Zr₄₆Al₄Ti₄and Cu₄₆Zr₄₅Al₈Ti₁by adding Ti element. Theamorphous structure and thermodynamic properties were characterized by X-raydiffraction and DSC, respectively. Furthermore, the room temperature compressionproperties was also investigated. The electrochemical behavior of amorphous alloy in3.5%NaCl and1mol/L NaOH solution was also investigated, using anelectrochemical method. The conclusions are listed as follows:（1） Cu₄₆Zr₄₆Al₄Ti₄and Cu₄₆Zr₄₅Al₈Ti₁bulk amorphous alloy were successfullyprepared. The T_xand ΔT_xof both alloys are reduced, suggesting that the glass formingability is reduced. Compared with amorphous alloy Cu₄₆Zr₄₆Al₄Ti₄, Cu₄₆Zr₄₅Al₈Ti₁has better thermal stability.（2）Both the two amorphous alloy have fractured after elastic deformation,without significant plastic deformation. The fracture strength of Cu₄₆Zr₄₆Al₄Ti₄is1795MPa, which is12%higher than that of Cu₄₆Zr₄₆Al₈, indicating that a very smallamount of Ti element can significantly improve the fracture strength of amorphousalloys. The fracture strength of the Cu₄₆Zr₄₅Al₈Ti₁is1650MPa, which is basically thesame as Cu46Zr46A18. For amorphous alloy Cu₄₆Zr₄₆Al₄Ti₄, the increase of adiabatictemperature in the cross-section is different when it fractures, which results in avariety of different fracture morphology. The melting regions and vein patterns revealthat amorphous alloy release a lot of strain energy when it fractures, which results in alarge adiabatic temperature rise in the cross-section. The reasons of the formation ofsmooth featureless zone is probably that the viscosity of the fracture section doesntchanges significantly due to the small temperature rise, so it is hard to form veinpatterns. The section surface of amorphous alloy Cu₄₆Zr₄₅Al₈Ti₁has not only vein-likepattern morphology but also a large number of droplet and molten region, and the areaof brittle fracture region is big. The amount of vein-shape and river-like pattern is few,indicating that he plasticity of the amorphous alloys is poor.（3） The alloy Cu₄₆Zr₄₆Al₄Ti₄containing quenched crystals has occured acatastrophic fracture when it reachs the stress limit, wich was known as brittle fracture.Its ompressive fracture strength is1303MPa, which is much lower than that of Cu₄₆Zr₄₆Al₄Ti₄amorphous alloy. There are a variety of morphology in its surface,most of them are brittle fracture zone. Both the amorphous part and crystal part of thealloy affect the fracture behavior of amorphous alloy, resulting in a mixture of ductileand brittle fracture mode. The bonding interface between the crystalline phase andamorphous matrix is the the stress concentration zone, where is easy to form crack andmake crack propagation. The fracture behavior of Cu₄₆Zr₄₅Al₈Ti₁containing crystal isthe similar with Cu₄₆Zr₄₆Al₄Ti₄.（4） The polarization curve test results showed that the corrosion current ofCu₄₆Zr₄₆Al₄Ti₄bulk amorphous alloy is one order of magnitude smaller than that ofCu₄₆Zr₄₆Al₈in3.5%NaCl solution, while the decrease amplitude of corrosion currentof Cu₄₆Zr₄₅Al₈Ti₁is smaller. The result of electrochemical impedance spectroscopy isin accord with the polarization curve. The experimental results showed that thecorrosion resistance of Cu₄₆Zr₄₆Al₈amorphous alloy corrosion resistance has beenimproved by adding a small amount of Ti element, and the corrosion resistance ofCu₄₆Zr₄₆Al₄Ti₄is better than that of Cu₄₆Zr₄₅Al₈Ti₁. The analysis shows that Ti canlower the the corrosion current by suppressing the cathodic process, which results inthe decrease of corrosion speed. The mechanism is possible that the addition of Ti canreduce the area of active cathodic or increase the overpotentail of the ionization ofoxygen. The results of polarization curve and electrochemical impedancespectroscopy in1mol/L NaOH solution showed that the corrosion resistance ofamorphous alloy was not significantly changed by replacing Al with Ti. It is probablybecause the amorphous alloy has high corrosion resistance itself, so no significanteffect is observed in the corrosion resistance of the amorphous alloy when adding Tielement.