First Principle Study Of Mechanical Property And Elements Doping Of Laves Phase TaCr₂

Laves phase TaCr₂ has high melting point, moderate density, excellent oxidation resistance and creep resistance at high temperature. But the serious room temperature brittleness hinders its application in aerospace field. In this paper, the phase stability and mechanical properties of Laves phase TaCr₂ and X（X=Fe、Si、Mo、Ti） doping of TaCr₂ are investigated theoretically by the first-principle method. The above theoretical research can give an important theoretical basis for solving the room temperature brittleness of Laves phase TaCr₂ and the optimum design of Ta-Cr alloys.Firstly, the mechanical properties, phase stability and electronic structures of Laves phase TaCr₂ are investigated by the first-principles calculations. The results show that the C15 and C14 structures of Laves phase TaCr₂ match the restrictive conditions for the stability of mechanical properties, and the C15 structure is more prone to elastic deformation than C14. Meanwhile, C15 is generated easier than C14,and C15 is more stable than C14. Meanwhile, the electronic structures of C15 and C14 are calculated. The C15’s Fermi energy is much lower than the C14’s. This result shows furtherly that C15 is more stable than C14. For the density of states, TaCr₂ presents a significant wider pseudogap, and the hybridization effects between the compounds are more strongly. The strong hybridization effect between Ta and Cr atoms increases the bonding directionality, which is bad for TaCr₂ toughness. This could be one of the reasons for the serious room temperature brittleness of Laves phase TaCr₂.Then, The mechanical properties, phase stability and the electronic structures of X（X=Fe、Si、Mo、Ti） doping of C15 structure TaCr₂ are investigated by first-principles calculation. The calculated results show that Fe and Si atoms primarily substitute on Cr sites, Mo and Ti atoms primarily substitute on Ta sites in TaCr₂, Which is consistent with experimental result. Mo and Ti atoms primarily substitute on Ta sites and Si atoms substitute on Cr sites can stabilize phase stability of TaCr₂. Meanwhile,Fe atoms substitute on Ta sites decrease phase stability of TaCr₂.Finally, the mechanical property of the binary and ternary Ta Cr₂ are investigated.The results show that: The elements of X（X=Fe, Si, Mo, Ti） doping increases the hardness of TaCr₂, In these elements,the most increase the hardness of TaCr₂ is Ti doping. Fe, Si and Mo doping can improve the brittleness of TaCr₂, WhereFe doping is the most effective to the brittleness of TaCr₂, Meanwhile, Ti doping reduce the toughness of TaCr₂, This is consistent with the results of electronic structure analysis and the experimental results. and after X doping, TaCr₂ are likely to produce micro crack in the process of crystal growth, In these elements, Si, Mo and Ti doping TaCr₂ haveincrease the likely to produce micro crack, while Fe doping TaCr₂ have reduces the likely to produce micro crack. In summary, in the elements Mo, Si, Fe and Ti, Fe doping is the most favorable to improve the brittleness of TaCr₂.