Effect Of Doping Elements On Titanium Alloys'mechanical Behaviors Based On The Study Of Generalized Stacking Fault Energy

With the advantages of high strength-weight ratio,corrosion resistance,outstanding thermal properties and good biological compatibility,titanium alloys were widely used in aerospace,shipbuilding,biomedical and automobile.In the high speed deVelopment of industrial process,titanium alloys has played an important role.HoweVer,due to titanium belongs to close-packed hexagonal(HCP)type metals,which have less slip system compared to face-centered cubic and body-centered cubic,resulting in its worse plasticity and ductility.In order to solve this problem,material researchers have done a lot of work to improve titanium's poor plasticity through experiments and simulations.Among these work,doping different elements into titanium alloys to improve its mechanical properties is commonly used and proved effectively.Based above,in this work,we detect the influence of different doping elements on the generalized stacking fault energy(GSFE)by using the first-principles-density functional theory.From the calculation results,the best doping element for titanium is concluded.Moreover,the electron structure of titanium and alloying atoms is described by the electron density distribution and the deformation mechanism for different doping systems was analyzed from a microscopic perspective.It will provide theoretical principle and methods for fabricating excellent titanium alloys by experiments.The research contents are listed below:1.The influence of both 8 kinds of substitutional atoms including Hg,Pb,Pd,Si,Sn,W,Zn,Zr and 4 kinds of interstitial atoms including C,H,O,N on the generalized stacking fault energy was studied by the first-principle calculation.By using the ratio of stable stacking fault energy(?SF)and unstable stacking fault energy(?USF),the influence of doping elements on deformation mod is estimated.By using the ratio of unstable twinning energy(?UT)and unstable stacking fault energy(?USF),the influence of doping elements on tendency of stacking fault and twinning is concluded.2.By the calculation results of surface energy(ys)for different doping systems,the influence of doping elements on titanium alloys' mechanical properties can be estimated.?s is taken as the energy barrier to create a new surface,which represents the ability of resistance the crack propagation.It can be taken as the criterion for assessing fatigue strength.Moreover,the ratio of ?S/?USF can be used to assess the plasticity for different doping systems.The calculation results reVealed that Ti-W system shows a best balance between strength and plasticity.3.By detecting the electron density distribution for different doping systems,the influence of alloying elements on titanium's mechanical behavior is analyzed from a microscopic perspective.It is reVealed that the doping elements made the electrons transfer from titanium atoms to doping atoms,resulting in the reduction of interaction between titanium atoms.It is the essential reason why the alloying elements influence the GSFE,and then influence the deformation behavior of titanium.