Influence of doping concentration on mechanical properties of Mo2FeB2 alloyed with Cr and Ni from first-principle calculations

The structural, elastic properties, hardness and electronic structure of Mo2FeB2 alloyed with Cr and Ni have been investigated by using first-principles calculations. The doping concentrations of 2.5 at. %, 5.0 at. %, 10.0 at. % and 20.0 at. % are analyzed systematically in this paper. From the calculated impurity formation energy, it is found that all the structures can retain good structural stability with the doping concentrations of Cr, Ni up to 20.0 at. %. According to the calculated elastic constants, it is observed that Cr can increase the Young’s modulus and hardness and reduce the ductility of Mo2FeB2 markedly with the increasing of alloying concentration. In contrast, Ni can decrease the hardness but improve the ductility of Mo2FeB2 obviously. The calculated electronic structure indicates that the increase of elastic modulus is attributed to the formation of BCr bond for Cr-doped and BNi bond for Ni-doped. The MoCr and MoNi metallic bonds weaken the shear modulus of Mo2FeB2. When the doping concentration is 20.0 at. %, it is obvious that the alloying elements Cr and Ni can significantly affect the moduli of Mo2FeB2.