Enhanced mechanical properties of W-doped Nb4AlC3 ceramics

The W-doped Nb4AlC3 ceramics [(Nb1-xWx)4AlC3, x = 0-0.0375] were successfully fabricated by in-situ reactive hot-press-aided method using elemental niobium, aluminum, graphite and tungsten powders. The XRD results suggest that the matrix phase (Nb1-xWx)4AlC3 and the second phase (Nb1-xWx)C were simultaneously formed when W was added. The SEM images show that (Nb1-xWx)C is dispersed in the W-doped Nb4AlC3 ceramics matrix. The mechanical properties of Nb4AlC3 were greatly enhanced by W doping. Typically, the (Nb0.975W0.025)4AlC3 exhibits the highest flexural strength (483 ± 21 MPa), fracture toughness (8.5 ± 0.3 MPa⋅m1/2) and Young′s modulus (382 ± 18 GPa) at room temperature (RT), which are increased by 59%, 15% and 30%, respectively, compared with the present Nb4AlC3. The Vickers hardness of (Nb0.9625W0.0375)4AlC3 (4.8 ± 0.2 GPa) is 92% higher than that of Nb4AlC3. The (Nb0.975W0.025)4AlC3 also retains a high flexural strength of 344 ± 4 MPa at 1400 °C (71% of RT value), which is much higher than the RT flexural strength (303 ± 22 MPa) of the present Nb4AlC3. The strengthening effect is attributed to the solid solution of W and the incorporation of the second phase (Nb1-xWx)C. The excellent mechanical properties endow the W-doped Nb4AlC3 ceramics as promising high-temperature structural materials.