Effect of doping Al, Ni and Zr on the properties of TiB2 coatings: A first-principles study

Abstract

The crystal structure, elastic constant, band structure and density of states of the (Ti 1- x M x )B 2 ternary coatings (M=Al, Ni, Zr) obtained by doping metal elements in the lattice of TiB 2 are calculated by the first principles based on the density functional theory. The results show that when Ti atoms in the lattice of TiB 2 are partially replaced by Al, Ni and Zr atoms, the cell volume and the binding energy of the (Ti 1- x M x )B 2 ternary coatings increases. With the increase of dopants, the structural stability of (Ti 1- x M x )B 2 ternary coating decreases. The binding energy proves to be positive when the content of dopant Al reaches 3% and that of Ni is more than 13%. However, the binding energy is still negative even that of Zr is more than 25%. The dopants (Al, Ni and Zr) reduce the hardness (7.7%, 10% and 8.6%, respectively) and improve the toughness of the TiB 2 coating (4.7% reduction in G / B ratio). Due to more obvious weakening of the orbital hybridization of Ti(Ni) and B atoms, Ni-doping has more significant effect on reducing the hardness of TiB 2 coating. • The structural stability of TiB 2 coating is reduced by doping Al, Ni and Zr. • The minimum effect of dopant Zr on the structural stability is observed. • The dopant Ni results in a 10% reduction in the hardness of TiB 2 at most. • The toughness of TiB 2 has been enhanced by doping Al, Ni and Zr.