Influence of Dy and Ho on the Phase Composition of the Ti-Al System Obtained by ‘Hydride Technology’

The manuscript describes the phase composition, microstructure, some physical and mechanical properties of the Ti-Al system with addition of 2 at. % Dy (TAD) and Ho (TAH) obtained by “hydride technology”. Phase diagrams for Ti-Al-Dy and Ti-Al-Ho at a temperature of 1150 °C and basic properties for ternary phases Dy₆Ti₄Al₄₃ and Ho₆Ti₄Al₄₃ were calculated. A crystallographic database of stable and quasistable structures of the known elemental composition was created in the USPEX-SIESTA software by means of an evolutionary code. The calculations show that adding REM leads to a significant stabilizing effect in each Ti-Al-Me (Me = Dy, Ho) system without exception. It has been established that the lattice energies of AlTi(3)Ho and AlTi(3)Dy are, respectively, equal to: EAl(4)Ti(12)Dy(3) = −32,877.825 eV and EAl(4)Ti(12)Dy(3) = −31,227.561 eV. In the synthesized Ti(49)Al(49)Ho(2) compound, the main phases include Al-Ti, Al(3)Ti(3) and Al(4)Ti(12)Ho(3) and the contributions to the theoretical intensity are equal to 44.83, 44.43 and 5.55%, respectively. Ti(49)Al(49)Dy(2) is dominated by the Al-Ti, Al(3)Ti(3) and Al(4)Ti(12)Dy phases, whose contributions are equal to 65.04, 16.88 and 11.2%, respectively. The microhardness of TAD and TAN specimens is 1.61 ± 0.08 and 1.47 ± 0.07 GPa, respectively.