| Titanium alloy is a new type of light alloy material with excellent comprehensive mechanical properties such as corrosion resistance,high temperature resistance,non-magnetic and non-toxic,small density and high strength.It is widely used in aerospace,deep sea exploration and marine engineering equipment as a key core material.In recent years,the excellent performance of ?-titanium alloy as a human implant has attracted much attention in the field of biomedicine.Therefore,the development and design of ?-titanium alloy with both high strength and low elastic modulus has become one of the research focuses.To obtain the expected mechanical properties,the development of high-performance titanium alloys requires strict control and rational design of titanium alloy components and structures.It is a comprehensive result based on the quantitative relationship between alloy composition,structure,performance,and process.The composition and concentration of the alloy are the key to the design of the alloy.It has a crucial influence on the structure and grain size of the alloy,which determines the comprehensive mechanical properties of the titanium alloy.Meanwhile,the alloy interface is also one of the important factors that affect the properties of the alloy.In the industrial production and preparation of titanium alloys,a large amount of hydrogen elements often accumulate near the grain boundaries to cause embrittlement of the material.The segregation of hydrogen in the grain boundary leads to the grain boundary often serving as a channel for crack generation and crack propagation,which significantly deteriorates the strength of the alloy and seriously affects the mechanical properties of the alloy.Therefore,exploring the distribution,diffusion,and segregation of hydrogen elements in the titanium alloy near the grain boundaries of the titanium alloy is extremely important for understanding the hydrogen embrittlement phenomenon in the titanium alloy.To sum up,through the first-principles method based on density functional theory,the elastic properties of titanium alloys and the hydrogen embrittlement in the grain boundaries are studied.(1)The elastic properties of binary ? titanium alloy.Through the first-principles method,we systematically investigated the influence of transition metal(including 3d,4d and 5d metal elements)composition and its concentration on the elastic modulus of titanium alloy.We found that the binary alloy composed of niobium and titanium has the lowest Young's modulus,which is consistent with the fact that titanium-niobium alloys are often used as the main component of artificial bones.At the same time,it is predicted that the homologous metals iron,ruthenium and osmium have extremely high elastic properties,and the low price of iron makes the alloy with titanium have extremely high development value for use in aerospace,deep sea exploration and other fields.(2)Hydrogen embrittlement in the grain boundaries of titanium.Using first-principles and under the framework of Rice-Wang thermodynamic model,the embrittlement phenomenon caused by the interaction between titanium grain boundaries and hydrogen was comprehensively studied.We confirmed that the hydrogen is a strong intergranular embitter with a potency of 0.817 e V/atom.Through the analysis of the electronic structure and bonding characteristics,it is found that titanium and hydrogen atoms on the grain boundary plane form a strong covalent bond,wherein the hydrogen atom obtains a charge of about 0.65 ev,but the titanium-titanium bond is perpendicular to the grain boundary was greatly weakened.Therefore,the weakening effect of hydrogen is due to the weakening of the titanium-titanium bond that maintains the cohesive force of the grain boundary,thereby significantly reducing the cohesive force of the grain boundary.This work provides a new understanding of the embrittlement phenomenon caused by the interaction between hydrogen and titanium grain boundaries at the electronic level. |
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