Systemically Study Of Electronic Structure And Properties For Ti-Al Alloys

In this works the Ti-Al alloys high-temperature structural materials have been systemically studied and analyzed. The electronic structures and properties of pure metal Ti with different crystal structure have been studied by using the one-atom (OA) theory, and the reasons of the forming of different crystal structures have also been analyzed. The electronic structures and properties of Ti-Al alloys have been systemically studied and analyzed by using the characteristic crystal (CC) theory, the lattice, atomic energy, electronic structures and properties of the characteristic atom or characteristic crystal with fcc and hcp structure have been determined. The equation of Gibbs energy and the equation of volume in CC theory have been determined and the properties of alloys have been obtained. And the effects of concentration on the properties of the alloy and its components have been calculated. The CC theory have been applied to the systemically study and analyses of the TiAl, Ti3Al and TiAI3 ordered alloys. The equations of Gibbs energy and the equation of volume in CC theory of the ordered phase in Ti-Al system have been determined.The cohesive energy~ atomic volumes, electronic structures and the properties of TIAI, Ti3AI and TIAI3 ordered alloys have also been calculated and their cohesive energies and atomic volumes were in good agreement with the experimental values. It was known from the results that the cohesive energy of the ordered phase is obviously higher than that of the disordered alloy at the same concentration, which shows the obvious tendency of ordered. The effects of the concentration and the degree of order on the structures and properties have also been studied and analyzed. The relationship between the alloy抯 properties and the concentration, and the contribution of the component have also been calculated and their curves were given. It was known according to the analyses that there were a strong effects between the Ti-d and Al-p electron and these electrons shows strong direction which lead to the dis-uniform distribution of electrons on the bond between atoms, it was very difficult to slip because of the higher energy barrier, so the alloys shows brittleness. And the higher proportion of the covalent electrons may be also have contribution to the brittleness of the alloys. The effects and selection of the third component have been analyzed. The curves of thermodynamics, atomic volumes, electronic structures and the curves of the properties have been given, which supply the foundation for the design of Ti-Al. The stabilization of the crystal structure TiAI, Ti3AI and TiAl3 ordered alloys have been studied by single atom manipulation, the effects of concentration, boundary and alloy element on the properties of TiAl alloy have been analyzed by clusters method.