Effects of alloying elements such as Ti, Zr and Hf on the mechanical and thermodynamic properties of Pd-Base superalloy

From first-principle calculations with the Local Density Approximation (LDA) and Generalized Gradient Approximation (GGA) approaches, the structural, elastic, electronic and thermodynamic properties of the PdTM and Pd31TM(TM = Ti, Zr, Hf) alloy have been investigated in this work. The calculated cohesive energy and formation enthalpies of these alloys, the PdZr and Pd31Zr have the lowest formation enthalpy with −0.57 and −0.13 eV/atom, respectively. It is calculated the elastic constants of crystal, bulk shear, Young's modulus and Poisson's ratio of the PdTM and Pd31TM(TM = Ti, Zr, Hf) compounds. The elastic constants show that these alloys are mechanically stable, and PdTi has the largest shear modulus and Young's modulus within 103.2 GPa and 36.9 GPa, respectively. Pd31Ti also has the largest shear modulus i.e. 70.5 GPa, and Pd31TM (TM = Ti, Zr, Hf) compounds have almost similar Young's modulus. The anisotropic mechanical properties of the PdTM and Pd31TM(TM = Ti, Zr, Hf) are discussed by the anisotropic index, three-dimensional (3D) surface contours and the planar projections on (001) and (110) planes of the Young's modulus. Vogit and Reuss method are used to estimate the effects of different concentrations of transition elements on the mechanical properties. The electronic structures and chemical bonding characteristics are analyzed by the band structures and the density of states. When compared with Ni-Base superalloys, Pd-Base alloys have excellent properties with great potential application as next generation superalloy at higher temperature.