Gigapascal yield strength at 900 °C in a boron-free TiAl complex alloy having excellent room temperature formability

A newly designed boron-free alloy, Ti<inf>50</inf>Al<inf>45</inf>Nb<inf>2.5</inf>Mo<inf>1.25</inf>Ta<inf>0.5</inf>W<inf>0.5</inf>V<inf>0.25</inf> (TiAl–complex alloy (CA), ρ = 4.12 ± 0.015 g cm−3), exhibited a compressive yield strength (YS) of 1.080 ± 0.029 GPa at 900 °C, along with excellent room temperature (RT) strength–formability (YS = 1.107 ± 0.038 GPa, ε = 0.12 ± 2) synergy in the as-cast state. Moreover, the as-cast TiAl CA exhibited controlled mass gain (1.46 ± 0.07 mg cm−2) at 900 °C upon isothermal exposure for 96 hours, displaying excellent oxidation resistance. The improved strength–formability synergy at RT is attributed to a refined γ-L1<inf>0</inf>-dominated three-phase microstructure undergoing twinning and deformation-induced (γ → α<inf>2</inf>) transformation, in addition to slip-based plasticity. The unusual yet desired β<inf>0</inf> phase dissolution (minimal phase fraction) at 900 °C provides exceptionally high YS, whereas the formation of dense Al<inf>2</inf>O<inf>3</inf> + TiO<inf>2</inf> layers on the surface results in controlled oxidation. Thus, the similar YS (∼1.1 GPa) of TiAl–CA at RT and 900 °C ensures exceptional microstructural stability in comparison with the pre-existing γ-TiAl and Ni-based superalloys, making it a potential candidate for fuel-efficient aero-engine applications. This journal is © The Royal Society of Chemistry, 2026