Study On Mechanical Properties And Electronic Structures Of Ti-V Alloys

This paper adopts the first principle calculation based on density functional theory,exchange correlation functional selects local density approximation?LDA?,the mechanical properties and electronic structures of three typical alloys of Ti-V alloys,D0₃-type Ti₃V alloy,B2-type TiV alloy and D0₃-type TiV₃ alloy were calculated.In addition,the structural stability and corrosion resistance of Ti-V-Cr ternary alloy system were calculated by electronic structure.The main conclusions are as follows:The mechanical properties and electronic structures of the three alloys are calculated as follows:?1?The calculation of cohesive energy and formation energy of the alloy system shows that TiV₃ structure is the most stable,followed by TiV,and Ti₃V structure is the least stable.Ti₃V has the strongest forming ability,followed by TiV,and TiV₃ has the weakest.The formation energy of the three alloys is negative,all three alloys are stable.?2?The calculation of self-interstitial formation energy shows that compared with Ti self-interstitial configuration,the self-interstitial configuration of V is easier to be formed.Either the self-interstitial configuration of Ti or the self-interstitial configuration of V,the TiV₃ self-interstitial formation energy is the largest.In addition,the self-interstitial formation energy of extruded columns is the lowest and the easiest.In the dumbbell configuration,the formation energy of<110>and<111>is low,and the configuration is stable.?3?The calculation of mechanical properties shows that the three alloys meet the mechanical stability standard of cubic structure.The bulk elastic modulus and shear modulus of TiV₃ alloy are the largest,indicating that the deformation capacity of TiV₃alloy is the weakest.All three alloys are ductile materials.The volume modulus and hardness calculations show that TiV₃ has the highest hardness,followed by TiV,and Ti₃V has the lowest hardness,which is consistent with the calculated results of self-interstitial formation energy.?4?The calculation of state density shows that the state density values of the three alloys at Fermi energy level are all greater than zero,showing obvious metallic characteristics and electrical conductivity.The state density of the three alloys at the Fermi energy level is mainly provided by the p and d orbital electrons of Ti,V.The three alloys show obvious hybridization to the left of Fermi level,indicating that all three alloys have obvious covalent properties.Based on the calculated state density and Fermi energy level analysis,it can be seen that the TiV3 alloy is the least vulnerable to lose electrons in the three alloys.From the mechanism of metal corrosion,it can be known that the TiV3 alloy has the best corrosion resistance in the three alloys.?5?The differential charge density calculation of the three alloys shows that the metallic bond is stronger than the covalent bond in the Ti3V alloy.Among the three alloys,with the increase of V content,the metallic property weakens,the covalency increases,and the alloy structure becomes stable.The calculation results of Ti-V-Cr alloy system are summarized as follows:?1?The structural stability of Ti-V-Cr alloy system by means of Ti atoms in Ti₃V alloy is replaced by Cr atoms was discussed.In Ti10V4Cr2 alloy with Cr content of12.50 at.%,the cohesive energy of the two Cr atoms corresponding to the position replacement of Ti atoms is quite different.When two Cr atoms are replaced by two Ti atoms in the second nearest neighbor,the cohesive energy is the lowest and the structure is the most stable.When the other positions are replaced,the cohesive energy increases and the structural stability weakens.For other kinds of Ti-V-Cr alloy systems with Cr content,Cr atoms replace Ti atoms have little effect on the structural stability.?2?It can be seen from the calculated cohesive energy that adding a small amount of Cr element to Ti₃V alloy increases the cohesive energy slightly and decreases the structural stability slightly.However,with the increase of Cr content,the cohesive energy increases rapidly,indicating that in the Ti-V-Cr alloy system,the higher Cr content,the more detrimental to the structural stability of the alloy system.However,the formation energy of the alloy system is all negative,indicating that the formed alloy can be stable.?3?Ti3V alloy without Cr element has the highest Fermi energy level.Cr content is within the range of 25 at.%(Ti_12-xV₄Cr_x?x=1-4?).With the increase of Cr content,the Fermi energy level of the alloy system decreases successively.The less likely an alloy system is to lose electrons,the corrosion resistance of the alloy system is enhanced.?4?The calculated results of the state density of the alloy system show that with the increase of Cr content,the pseudoenergy gap and hybridization of the alloy system gradually disappear,the covalent characteristic of the alloy system weakens,and the structural stability of the alloy system decreases,which is consistent with the calculated results of cohesive energy.Secondly,with the increase of Cr content,the peak value of state density in the whole energy range moved to the direction of lower energy,and the state density value at Fermi energy level significantly decreased,indicating that the electrons in the alloy system became stable and could not easily lose electrons,and the corrosion resistance of the alloy system increased.