Synthesis of Nb2AlC MAX Phase by SHS Metallurgy

A cast material based on the Nb 2 AlC MAX phase is formed by SHS metallurgy. The synthesis is performed using the Nb 2 O 5 –Al–C mixture with the CaO 2 –Al high-energy additive. The results of thermodynamic calculations correlate with the experimental data. The substantial influence of the CaO 2 –Al additive on the thermodynamic parameters and phase composition of the product is established. It is shown that the synthesis using mentioned mixtures occurs in a stationary mode with the formation of a steady combustion wave. The combustion rate increases from 6 to 12 mm/s with an increase in the additive content, and the product yield into the ingot increases from 30 to 47% (up to 15 wt % additive) and then decreases. The variation in the composition of initial mixtures can substantially affect both the synthesis parameters and the phase composition of products. The optimal synthesis conditions of the materials that provide the maximal yield of the Nb 2 AlC MAX phase in the ingot composition are established. The determining factor that affects the Nb 2 AlC content in the product is the liquid-phase lifetime under the synthesis conditions. It is shown that the maximal amount (67 wt %) of the Nb 2 AlC phase is attained with the content of the high-energy additive in the initial charge of 15 wt %.