Study On Mechanical And Thermal Properties Of W_x（TaTiVCr）_1-x

Controlled nuclear fusion can be regarded as an ideal energy source which has attracted worldwide attention.However,the complex working environments in nuclear reactors have strict demands on materials.Although the application research has made great progress after years of exploration,the development of relevant materials has always been a hot issue in determining the performance of nuclear fusion reactor.High entropy alloys(HEAs)are a new class of material in material science and engineering and can possess special properties,including high strength/hardness,exceptional high-temperature strength,good corrosion and oxidation resistance.So HEAs,as superior nuclear,functional and structural materials,are considered to have a wide range of applications in the transportation,aerospace and military industry.Tungsten and its alloys have excellent thermodynamic properties(such as high temperature,high melting point and excellent thermal conductivity),and are generally considered to be the most promising candidate materials in nuclear industry.In the present work,the mechanical and thermodynamic properties of Wx(TaTiVCr)1-x are studied and discussed in depth using the first-principles,the main research contents are as follows:Firstly,mechanical and electronic properties of high entropy(-like)alloys Wx(TaTiVCr)1-x、(x=0.30-0.67)with body centered cubic structure are investigated employing density function theory in combination with special quasi-random structure(SQS)model.The results show that with simultaneous addition of multi-principle alloying elements with smaller average of atomic radii,the lattice constants drop slightly,and structural stability is somewhat lowered due to the higher formation enthalpies.The calculated elastic stiffness constants and elastic moduli derived within the Voigt-Reuss-Hill approximation suggest the noticeable decrease of hardness and strength of the Wx(TaTiVCr)1-x(x = 0.30-0.67)alloys.Interestingly,ductility of Wx(TaTiVCr)1-x(x = 0.30-0.67)alloys is apparently increased,whereas elastic anisotropy is somewhat larger from several criterions.The further studied electronic structures show that bonding of Wx(TaTiVCr)1-x(x = 0.30-0.67)dominantly originates from the contributions of d electrons of constituent elements,W-W bonding is stronger than W-M(M = Ta,Ti,V,Cr)and M-M interactions(M = Ta,Ti,V,Cr).With simultaneous addition of multi-principle alloying elements,values of DOSs at Fermi level are higher and the interplay between atoms is decreased,showing the lower stability.These results provide a guideline for further optimizing the composition and mechanical properties of tungsten alloy.Secondly,based on quasi-harmonic Debye-Gruneisen model and thermal equation of state,thermodynamic properties of high entropy(-like)alloys Wx(TaTiVCr)1-x(x = 0.30-0.67)phases have been studied by first principles density functional theory calculations combined with special quasi-random structure(SQS)model,and influence of W content is predominantly emphasized.Present investigations show that bulk modulus B of Wx(TaTiVCr)1-x declines with increasing temperature,and the softening tendency is similar for various W content,although the strength of Wx(TaTiVCr)1-x demonstrates overall lowering with simultaneous alloying of Ta,Ti,V and Cr.The thermal expansion coefficient rises Wx(TaTiVCr)1-x nonlinearly with increasing temperature,and the increase rate is lowered with more W content.The temperature dependence of heat capacity at constant volume Cv and constant pressure Cp of Wx(TaTiVCr)1-x also exhibit analog behavior at various W content.Thermodynamic entropy of Wx(TaTiVCr)1-x increases dramatically with temperature,and the contribution from electronic entropy,configuration and vibrational entropy is discussed in details.In addition,the Debye-temperature and Gruneisen parameter are also analyzed.The present results are very valuable for optimizing the composition and comprehensive properties of W-containg high entropy(-like)alloys.