Preparation,Structure And Properties Of Ti-Zr-Y Ternary Alloy

Titanium(Ti)and their alloys have many excellent properties,such as low density(only approximately half that of steel and nickel-based superalloy),high specific strength,excellent biocompatibility,good corrosion resistance and fatigue resistance,thereby making titanium-based alloys permeate in marine,military,aerospace,automotive engineering,chemical,biomedical and other fields.Due to the same subgroup(IVB)of Zirconium(Zr)and Ti in the periodic table of elements,they show similar chemical properties and structure.Both elements have high corrosion resistance due to the formation of passive films.The addition of an appropriate amount of Zr can increase the strength and elevate the corrosion resistance of Ti alloys.Therefore,development of Ti Zr-based alloys as corrosion-resistant structural materials materials has significant potential.However,the strength of traditional Ti Zr binary alloys is relatively low.It is necessary to continue to research new alloys to further develop Ti Zr-based alloys in structural applications.Adding alloying elements is an effective method to improve the structure and properties of Ti Zr-based alloys.The effects of Y content on the microstructure,mechanical properties and corrosion resistance of as-cast and hot-rolled Ti-25 Zr alloys were systematically studied in this paper.The relationship between the microstructure morphology,mechanical properties and corrosion resistance of Ti-25Zr-0.4Y alloy at different annealing temperatures was also investigated.The ingots of Ti-25Zr-xY were prepared under the argon atmosphere and cooled in water-cooled copper crucibles by a vacuum non-consumable electrode arc melting technique.DSC,XRD,OM,SEM,TEM,electrochemical workstation and tensile test were employed to investigate the microstructure mechanics and corrosion properties of these alloys.The results show that the microstructure of the as-cast alloy can be significantly refined by adding trace rare earth Y elements.The refinement of prior-? grain was attributed to the constitutional undercooling,which was resulted from solute enrichment of Y in the liquid-solid interface.The addition of Y element thereby increased the grain-boundary range of the ? phase and provided more nucleation points for the ?-phase during ??? transformation.The compression strength was improved when the Y content is in the range of 0.4 at.%?0.8 at.%.All the alloys exhibited similar electrochemical corrosion behavior in 5 wt.%HCl solution.The corrosion resistance of the alloy was closely related to the amount of Y added,and Ti-25Zr-0.1Y alloy exhibited the best corrosion resistance.The Ti-Zr-Y ternary alloy was hot-rolled and deformed at 700°C(two-phase region).The results showed that Ti-25Zr-0.4Y alloy showed the best mechanical properties.The room-temperature tensile strength of the hot-rolled Ti-25Zr-0.4Y alloy was 932 MPa,and the elongation-to-fracture was 10.12%.Compared with as-cast alloy,rolling treatment improved the corrosion resistance of alloys with higher Y content(?0.2 at.%).This was because rolling treatment can redistribute the second phase particles in the matrix.The small and diffusely distributed second phase increases the randomness and uniformity of galvanic corrosion to a certain extent,which reduces the tendency of the alloy to pitting.At the same time,the microstructure and properties of the hot-rolled Ti-25Zr-0.4Y alloy were investigated at four annealing temperatures: 600 ?,700 ?,800 ?,and 900 ?.There was evidence that annealing treatment can improve the plasticity and corrosion resistance of the alloy.However,as the annealing temperature increased,the ? phase content and the size of the ?-lath in the alloy gradually increased,the plasticity of the alloy was improved,but the strength and corrosion resistance were continuously reduced.