Electronic structure and physical properties of hcp Ti 3Al type alloys

Abstract

According to the basic information of sequences of Ti and Al characteristic atoms in hep Ti-Al system, the compositional variations of the electronic structure, atomic potential energies, atomic volumes, lattice constants and cohesive energies of the ordered hcp Ti 3Al type alloys were calculated by the framework of systematic science of alloys(SSA). The electronic structure of the hcp Ti 3Al compound consisted of Ψ Ti 4h and Ψ Al Oh atoms is 0.75[Ar] (3 d n) 0.573(3 d c)2.1685(4 S c 0.972(4 S f ) 0.3093+0.25[Ne](3 s c ) 1.32, (3 p c ) 1.19 (3 Sf ) 0.49. The factors of controlling lattice stability are electronic structure, atomic energies and atomic concentration. The Ψ Ti 4h atoms play a determinative role in forming D0 19 structure with a=0.287 2 nm, c=0.456 4 nm, atomic cohesive energy ɛ=4.810 8 eV/atom and heat of formation Δ H=-0.332 8 eV/atom. These calculated values are in good agreement with experimental values ( a=0.287 5 nm, c=0.46 0 nm, Δ H=-0.27, -0.29 eV/atom). The calculated cohesive energy of the hep Ti 3Al compound is slightly bigger than that of the fcc Ti 3Al. This is a good sign that makes it feasible to stabilized L1 2 structure of the hcp Ti 3Al compound by ternary element. The new element should have more d c-electrons than Ti-metal and occupy at the Ti-lattice points.