Effect of alloying elements (Ni, Co, Cr, and Sn) on the mechanical properties of W-Cu alloy system predicted from first principles

In order to explore the reasons for the influence of alloying element X (X=Ni, Co, Cr, and Sn) on the strength, hardness and toughness of W-Cu alloy, this paper calculated the elastic constants and electronic structures of W-Cu alloy and W-X-Cu alloy based on first principles, and quantitatively evaluated the influence of alloying element X on the strength, hardness and toughness of W-Cu alloy from the atomic level. The results show that the W-Ni-Cu alloy system has the best strength and hardness when the doped content of Ni is 3.125%, and the alloy system has the best stiffness when the doped content of Cr is 12.5%. The electronic structure analysis shows that the charge density of Ni-3d, Co-3d, Cr-3d and Sn-5p orbitals increases with the increase of alloyed element doping ratio. Alloyed atom doping generates new chemical bonds in the system, and weakens the hybridization between Cu 3d and W 5d orbitals, thus affecting the bonding strength of W-Cu bonds. W-X bond is always a strong covalent bond, which can make up for the weakening of W-Cu bond to a certain extent. W-Cu bond and W-X bond jointly determine the strength and hardness of the system. Alloying atom X also changes the electron distribution on the 3d and 4 s orbitals of Cu atom, resulting in changes in the charge density between neighboring Cu atoms, which affects the toughness of the material system. [GRAPHICS] .