Effect of Nb addition on the microstructure and mechanical properties of additively manufactured Ti2AlC MAX-phase ceramic matrix composites

The Ti2AlC MAX-phase ceramic matrix composites were successfully additively manufactured from the Ti, Al, Nb and C elemental powders via laser powder bed fusion (LPBF) plus pressureless sintering (PLS) process. The phase formation, microstructure evolution, and mechanical properties of the as-fabricated samples were systematically analyzed under different Nb contents and sintering temperatures. The Nb content and sintering temperatures can significantly affect the phase formation and microstructure of samples. In the LPBF stage, all the samples are composed of TiC, Ti3Al, and TiAl, while adding Nb into the Ti-Al-C system powders can promote Ti2AlC MAX-phase. Furthermore, doping of Nb induce the transformation from Ti2AlC to Ti3AlC during the subsequent PLS. With increasing the sintering temperature from 1200 °C to 1400 °C, the width of Ti2AlC lamellar structure increases from 0.36 µm to 1.58 µm. The compressive strength of the Ti2AlC MAX-phase ceramic samples ranges between 17.5 MPa and 30.3 MPa. The optimal compressive strength of Ti2AlC MAX-phase ceramic matrix ceramic composite (30.3 MPa) was achieved under optimized Nb content (1 wt%) and sintering temperature (1300 °C). This work could shed light on designing Ti2AlC MAX-phase ceramic from the microalloying perspective via LPBF and sintering.