Theoretical Research On The Structures And Properties Of M(Zr, Nb And Mn) Doped ?-TiAl Based Alloys

The ?-Ti Al based alloys which formed by doping alloying elements is a kind of new material with potential application value. 16 ?-Ti Al based alloy systems have been formed with Zr, Mn and Nb single or double doped ?-Ti Al, and their geometric structures, energy properties, elastic properties, electronic properties and chemical bond properties are calculated and analyzed by using first-principles method based on the density function theory combined with physical chemistry theory. The results show that the stability of these systems as well as the probability of preparation at certain condition can be confirmed with their negative total energies and atomic average formation energies. Zr and(or) Mn doping can change the cubic degree of these kinds of ?-Ti Al based alloys particularly the ratios of axis of Ti12Al11 Zr, Ti12Al11 Mn, Ti11 Mn Al11Zr and Ti11 Zr Al11Mn systems are all close to 1, and the improvement is distinct. The change tendency of unit volume is in accordance with the radius of doping atom in these single-doping systems, while the change of unit volume is affected mainly by Zr and subordinately by Mn atom in these double-doping systems. Zr is inclined to substitute Ti atom, and Mn is inclined to substitute Al atom in single-doping systems while it has no trend to substitute Ti or Al atom. The calculation and analysis results about axis ratio, elastic modulus ratio show that the doping systems Ti12Al11 Zr, Ti12Al11 Mn, Ti11MnAl11 Zr and Ti11 Zr Al11Mn are all possess better ductility presenting theoretical supporting points for the efforts to improve the ductility of ?-TiAl based alloys. The metal conductivity of systems Ti12Al11 Zr, Ti11MnAl11 Zr and Ti11 Zr Al11Mn are confirmed by their band structures. Similarly, Zr and(or) Nb doping can change the cubic degree of ?-Ti Al based alloys too and Nb is always inclined to substitute Ti atom. The doping systems of Ti12Al11 Nb, Ti11 Nb Al11Zr and Ti11 Zr Al11Nb have better ductility and metal conductivity. Based on the examination of density of states and overlap population of these alloy systems, it was presented that the doping of Zr, Mn and Nb make the decreased intension of covalent bond while the increased intension of metal bond, resulting in the stability of these alloy decreased slightly. Therefore, it can improve the mobility of the crystal face, which is favorable for improving the ductility of the alloys.