The precipitation processes of the γ1 phase in Ti–53Al–18Nb alloys

First-Principles Calculations on Structural Property and Anisotropic Elasticity of γ1-Ti4Nb3Al9 under Pressure

“…It has been proven that Nb atoms in $\gamma$-TiAl substitutes for Ti atoms and preferentially occupies the Ti sublattice [2]. Some experimental studies on phase relationship for the alloys showed that the continuous ordering of Nb atoms in the Ti sublattice of $\gamma$-TiAl appears with increasing Nb content, resulting in the Nb atoms to occupy specific Ti sublattices to finally form a new ternary ordered phase named ${\gamma }_1$[3,4,5,6,7,8,9]. The ${\gamma }_1$ phase has been confirmed as a stable phase [4,5,6,7,8,9].…”

“…Some experimental studies on phase relationship for the alloys showed that the continuous ordering of Nb atoms in the Ti sublattice of $\gamma$-TiAl appears with increasing Nb content, resulting in the Nb atoms to occupy specific Ti sublattices to finally form a new ternary ordered phase named ${\gamma }_1$[3,4,5,6,7,8,9]. The ${\gamma }_1$ phase has been confirmed as a stable phase [4,5,6,7,8,9]. It has the determined chemical formula of Ti${}_4$Nb${}_3$Al${}_9$ and the tetragonal structure with space group $P4/mmm$, lattice constant a in the range of 5.58–5.84 Å and lattice constant c in the range of 8.15–8.45 Å [4,5].…”

“…It has the determined chemical formula of Ti${}_4$Nb${}_3$Al${}_9$ and the tetragonal structure with space group $P4/mmm$, lattice constant a in the range of 5.58–5.84 Å and lattice constant c in the range of 8.15–8.45 Å [4,5]. It has been revealed that the precipitation of ${\gamma }_1$-Ti${}_4$Nb${}_3$Al${}_9$ phase can inhibit dislocation motion on the slipping plane {111} of the $\gamma$-TiAl matrix, and thus improve the strength of high Nb containing $\gamma$-TiAl-based alloys [7,8,9,10]. The alloys with ${\gamma }_1$ phase have higher room-temperature and high-temperature strengths than those without ${\gamma }_1$ phase [11].…”