Theoretical Study On The Structures And Properties Of Mn Or(and) Y-doped ?-TiAl Alloys

The titanium-aluminum intermetallic compounds have good high-temperature performances, in which the ?-TiAl based alloy has become a potential aerospace material for its low density and high specific strength and creep resistance at high temperature. But its poor ductility at room temperature is a shortage besides its good overall performance, so many researchers are looking for methods to enhance its plasticity, and it has been found that alloying will be an efficient way.In this paper, based on the first-principles theories and using Materials Studio 6.1 software, Mn and Y single-doped and double-doped ?-TiAl alloy systems has been studied, with the concentration of dopant atoms selected being 1/16, 1/24,1/36 and 1/54 respectively. Properties calculated and analyzed include the lattice parameters, the average formation energy by atom, axial ratio, elastic modulus, band structure and overlap population, and so on, and the focus is how the stability and ductility of the doped ?-TiAl alloy vary with the change of the concentration of Mn and Y.Comprehensive analysis of the calculation results of the doping system indicates that the stability of Mn or Y single-doped ?-TiAl system are slightly lower than pure ?-TiAl system, and as the doping concentration decreases, the stability gradually increases. And Mn has higher possibility to substitute Al while Y is more likely to substitute Ti. The analysis of axial ratio and elastic modulus shows that single-doping of Mn or Y at an appropriate concentration will effectively improve the ductility of ?-TiAl alloy, with 1/24 the best atomic concentration for Mn and 1/16 the best atomic concentration for Y. As for the overlap population of the Mn or Y single-doped ?-TiAl compared with the pure ?-TiAl, it can be found that doping with Mn can weaken the anisotropy of the covalent bonds in ?-TiAl systems, which contributes partly to the ductility improvement of ?-TiAl alloys. As for the Mn and Y co-doped ?-TiAl systems, the stability and substitution rule is consistent with the single-doped system while the improvement of the ductility is more efficient, which be told by the axial ratio and explained by the overlap population.