The influence of niobium, tantalum and zirconium on the microstructure and creep strength of fully lamellar γ/α2 titanium aluminides

On the high creep strength of the W containing IRIS-TiAl alloy at 850 °C

“…For instance, in a recent systematic study performed in fully lamellar TiAl alloys containing 5% at. of Nb, Ta and Zr, Bresler et al [16] have demonstrated that, at 900°C, this hardening effect is resulting from solid solution hardening but also from the low diffusivity and solubility of these species in the  phase. The influence of incorporated tungsten atoms on the creep properties has been investigated in several studies (see for example references [17][18][19][20][21][22][23]), in particular in that dedicated to the alloys of the ABB family [19,20] and in that from the Otawa group [17,18].…”

Characteristic effects of alloying elements on β solidifying titanium aluminides: A review

“…Bresler et al. [ 65 ], showed that domain boundaries and interfaces of γ/γ phases diminishes the movement of dislocations and plastic deformation but not like the α 2 /γ interface. Since the γ and α 2 phases exhibit different slip systems, the movement of dislocations is restrained when compared to the γ/γ-interfaces.…”

“…The combined addition of Zr and Cr in TNM alloys promotes ω-phase formation by increasing β-phase and decreasing the amount of α 2 -phase [ 104 ]. It was also reported that Zr improves compressive strength [ 104 ], enhances fracture strain and yield stress at intermediate temperatures [ 65 ]. It has been reported that diffusion of Zr is much faster than Nb and consequently it has little benefit in retarding diffusion-controlled processes.…”

“…Bresler et al. [ 65 ], investigated the influence of Zr, Nb and Ta on the creep properties of Ti–44Al-5X (X = Zr, Ta, Nb) ternary alloy. The microstructure was reported to be fully lamellar microstructure.…”

“…The α 2 and γ phases display diverse behaviours during deformation owing to their distinctive crystal structures [ 63 ]. The Blackburn orientation relationship (BOR) expresses the crystallographic relationship between these phases [ 37 , 65 ]. A semi-coherent interface would result from any slight difference in the lattice parameters of both γ and α 2 phases.…”