Mechanical properties and oxidation behavior of Ti-doped Nb4AlC3

Herein, we present the first report on fully dense and phase pure (Nb1 − xTix)4AlC3 ceramics (x = 0–0.3), fabricated by in situ reaction hot-pressing method. The solid solution of Ti provides a significant strengthening effect to Nb4AlC3. Typically, (Nb0.8Ti0.2)4AlC3 exhibits the highest flexural strength (508 ± 28 MPa) and fracture toughness (8.4 ± 0.2 MPa m1/2), increasing by 47% and 18%, respectively. The Vickers hardness of (Nb0.7Ti0.3)4AlC3 (4.4 ± 0.2 GPa) is 69% higher than that of Nb4AlC3. The (Nb0.8Ti0.2)4AlC3 also retains a high Young’s modulus of 294 GPa at 1500 °C (84% of room-temperature value). Due to the formation of a more protective oxide scale consisting of TiNb2O7 and NbAlO4, the (Nb1 − xTix)4AlC3 exhibits a greatly improved oxidation resistance. Interestingly, a better oxidation resistance at 1000 °C and 1100 °C than at 800 °C and 900 °C was observed for (Nb1 − xTix)4AlC3. Excellent comprehensive properties render the (Nb1 − xTix)4AlC3 solid solutions promising high-temperature structural materials.