| At present,the high development of human society can not be separated from the support of natural energy,such as oil and natural gas,but the land natural energy is decreasing,and the research on alternative energy is not mature.The energy problem has become the important reason and restricts the development of society and economy.Under such circumstances,many countries have set their sights on the ocean with abundant natural resources and started developing marine engineering vigorously.Because of the special service environment,the selection of materials is very important for marine engineering.Ti80 alloy(Ti-6.0Al-3.0Nb-2.0Zr-1.0Mo)has excellent comprehensive properties such as high strength,high toughness,weldability and corrosion resistance.It is a widely used marine titanium alloy in our country.On the basis of the composition of Ti80 alloy,the composition of the alloy is optimized to further enhance its strength and corrosion resistance to cope with the more harsh marine engineering,such as deep sea oil and gas field mining.In this paper,the orthogonal experimental method was used to set up 16 groups of orthogonal experimental groups with four factors and four levels of Al,Nb,Zr and Mo.The mechanical properties and electrochemical corrosion properties of the alloys after vacuum annealing were calculated respectively.Then,the optimized component alloy was obtained by considering the Al-Mo amount criterion of the titanium alloy design.The performance of the optimized component alloy was verified through experiments,and studied on the microstructures and properties of the alloy components.The mechanical properties and electrochemical corrosion properties of the alloy after vacuum annealing were calculated respectively.Then,the optimized component alloy was obtained by considering the Al-Mo amount criterion of the titanium alloy design.The performance of each index was verified by experiments,and the microstructures and properties of the alloys were analyzed.By comparing the Ti-Al-Nb-Zr-Mo based alloy structure of each component,it is found that the phase composition of each component in the orthogonal group is the main phase ?-Ti and a small amount of ?-Ti,and the volume fraction of the ?phase is related to the content of the ? stable element in the alloy.The as-cast microstructure of each component alloy are mainly basket structure formed by staggered arrangement of ? layers with different orientations and sizes.With the increase of alloying degree,the microstructure becomes thinner and a small amount of needle like microstructure occurs.Al and Mo can play an important role in refining the microstructure of the alloy.After vacuum annealing,the microstructureof each component becomes coarse and homogeneous.The bending experiments showed that the room-temperature fracture toughness of Ti-Al-Nb-Zr-Mo alloys is good and it belongs to ductile fracture.The room-temperature compression experiments showed that Al,Nb,Zr,and Mo can all increase the strength of the alloy by solid solution strengthening.Al and Zr have a detrimental effect on the plasticity of the alloy.A certain amount of Nb and Mo contribute to the plasticity of the alloy.After the heat treatment,the room temperature compressive performance of all component alloys showed a decrease in strength and increased plasticity.Electrochemical corrosion tests showed that Nb,Zr and Mo can improve the corrosion resistance of titanium alloy by improving the passivation ability of titanium alloy,but when the beta stable elements such as Mo and Nb are added more,the beta phase increases,and the interphase potential difference will lead to the selective dissolution of the alpha phase and decrease the corrosion resistance of the alloy.The optimized component is Ti-5.5Al-3.0Nb-3.0Zr-1.2Mo,the heat treatment structure has a uniform net basket shape,and the mechanical properties and electrochemical corrosion performance are excellent.After adding 0.3wt.%Ni(Ti-5.5Al-3.0Nb-3.0Zr-1.2Mo-0.3Ni)to the optimized component alloy,the microstructure was refined,the compressive strength and the electrochemical corrosion properties were further improved,the fracture toughness and the plasticity were decreased. |
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