| The ocean is vast and rich in materials.The ocean is an indispensable trade channel and resource treasure house for all countries.The contemporary energy is declining and the energy in the ocean is huge.All countries pay special attention to the exploitation and utilization of the ocean and vigorously develop marine engineering in various countries.Due to the special service environment of the ocean,the material properties are more stringent.Ti90?Ti-4.09Al-3.9Zr-2.05Sn-1.5Mo-0.96Nb?alloy is a new type of titanium independently developed in China,which has the requirements of marine materials such as high strength,corrosion resistance,high toughness and workability.This paper will optimize on the basis of Ti90 alloy to obtain Ti-Al-Zr-Sn-Mo-Nb alloy with better performance,in order to better serve the marine industry.Firstly,the first principle principle virtual approximation method is used to design the alloy composition.According to the previous research of this group,the Al alloy content is determined to be5.5.Using CASTEP software to calculate the influence of the addition of alloying elements Zr,Sn,Mo and Nb on the lattice constant,elastic constant and density of state of Ti-5.5Al,the final range of alloying elements can be determined,Zr?1%4%??Sn?0.5%2.0%??Mo?0.3%2.0%??Nb?0.4%1.5%?.Four-level four-factor orthogonal experiment is designed according to the range of alloying elements obtained,and 16 sets of titanium alloys with different compositions are obtained.The 16 sets of titanium alloys are designed for microstructure observation,phase analysis,room temperature compression test,three-point bending test and electrochemical corrosion test.With these properties as indicators,combined with titanium alloy design criteria,the composition of the alloy can be optimized for optimization.Alloys are studied for organization and properties.Through the analysis of the microstructure and phase of 16 sets of orthogonally designed titanium alloys,it is found that the 16-component alloys belong to the near-?-titanium alloy,and the phase composition is?phase+a small amount of?phase.the thickness and uniformity of the structure is different,but The structure is a basket-like structure in which lamellar?-phases are interlaced in different orientations.The addition of Mo and Nb in the alloy can refine the grains.Appropriately increasing the degree of alloying of the alloy also allows the microstructure to be refined.The room temperature compression experiments show that the Ti-Al-Zr-Sn-Mo-Nb alloy has higher yield strength and better ultimate strain.The Al,Zr,Mo and Nb added in the alloy can be solid solution strengthened.The role of Mo addition has a beneficial effect on plasticity,and the plasticity of a certain amount of Sn has no effect.The fracture toughness test shows that the Ti-Al-Zr-Sn-Mo-Nb system has good toughness.The addition of Mo and Nb is beneficial to the improvement of fracture toughness value.The lamellar structure of the alloy makes the fracture toughness of the alloy better.Titanium alloy has excellent corrosion resistance.It can be seen from electrochem--ical corrosion experiments that the added Al will form Al2O3,which will protect the surface of titanium alloy,and Zr,Mo and Nb can improve the passivation ability of titanium alloy.Mo mass fraction not exceeding 1%will greatly improve the corrosion performance of titanium alloy.When the content of Mo and Nb is high,the content of?phase will increase,which will lead to selective dissolution of?phase,so the corro--sion resistance of the alloy will decrease,and Sn will combine with Cl ions in the etching solution to form insoluble oxychloride,which is not conducive to The corrosion resistance of the alloy.The optimized composition obtained by orthogonal experiment is Ti-5.5Al-4.0Zr-1.0Sn-0.3Mo-1.0Nb,which belongs to near-?-titanium alloy.The structure is a basket-like structure with even and fine interlamellar spacing.The mechanical properties of the alloy are the most.It has good corrosion resistance and good overall performance. |
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