First-Principles Calculations Of Mechanical And Thermodynamic Properties For Re-Ti-Si Intermetallics

Titanium and titanium alloys have been paid widespread attention in the aerospace, automobile manufacturing, biological material, military industry etc, due to its excellent physical and chemical properties such as high specific strength, high hardness, high plasticity, low elastic modulus and corrosion resistance. In the recent decades, addition of rare earth elements to enhance performance of titanium alloy is one topic of titanium materials investigations. Intermetallics of rare earth titanium silicon alloys RE-Ti-Si was one of the interested materials due to its unique properties. In this paper, the mechanical and thermodynamic properties of RE-Ti-Si intermetallic compounds were systematically studied by using the First-principles calculation method.Firstly, the First-principles calculation method were used to investigate the electronic structure, mechanical properties and thermal physical properties of GdTiSi and Gd2Ti3Si4, which are typical representative of RETiSi and RE2Ti3Si4, respectively. The ratio of bulk modulus and shear modulus B/G suggests that GdTiSi is ductile while Gd2Ti3Si4is brittle, and both of their properties are anisotropy. From the comparison of the results of the formation enthalpy, elastic properties and thermodynamic properties, one can see that Gd2Ti3Si4is strengther. harder and more stable than GdTiSi.Secondly, the phase stability, electronic structure, mechanical properties and thermodynamic properties of seven compounds of RETiSi (RE=Y, Tb, Dy, Ho, Er, Tm, Lu) were systematically calculated, and the change tendency of corresponding properties along with the increasing atomic number of rare earth element was discussed. The calculated lattice constants of RETiSi intermtallics show good agreement with the experimental data. Results show RETiSi compounds are ductile, and the strength and stability of compound slightly increase with the atomic number of rare earth element.Thirdly, results of phase stability, electronic structure, elastic properties and thermodynamic performance of four compounds of RE2Ti3Si4(RE=Tb, Dy, Ho and Er) were also systematically calculated, and the change tendency of corresponding properties along with the increasing atomic number of rare earth element was also analyzed. The calculated lattice constants are in good agreement with experimental results. Results show RE2Ti3Si4compounds are brittle. As the atomic number of rare earth element increases, the volume and formation enthalpy of compound decrease, while the bulk modulus, shear modulus and Young’s modulus increase slightly. This indicates that the strength and stability of RE2Ti3Si4intermetallics increase slightly with the atomic number of rare earth element.