Ti <sub>3</sub>AlC <sub>2− <i>y</i> </sub>N <sub> <i>y</i> </sub> carbonitride MAX phase solid solutions with tunable mechanical, thermal, and electrical properties
Abstract
Changing N content in Ti<sub>3</sub>AlC<sub>2-y</sub>N<sub>y</sub> MAX phase solid solutions allows for fine-tuning of their properties. However, systematic studies on the synthesis and properties of Ti<sub>3</sub>AlC<sub>2-y</sub>N<sub>y</sub> solid solution bulks have not been reported so far. Here, previously unreported Ti<sub>3</sub>AlC<sub>2-y</sub>N<sub>y</sub> solid solution bulks (y=0.3, 0.5, 0.8, and 1.0) were synthesized by hot pressing of their powder counterparts under optimized conditions. The prepared Ti<sub>3</sub>AlC<sub>2-y</sub>N<sub>y </sub>bulks are dense and have a fine microstructure with grain sizes of 6-8 μm. The influence of N content on the mechanical properties, electrical conductivities, and coefficients of thermal expansion (CTEs) of the prepared Ti<sub>3</sub>AlC<sub>2-y</sub>N<sub>y</sub> bulks has been clarified. Flexural strength and Vickers hardness values increased with increasing N contents, suggesting that solid solution strengthening is effective in improving the mechanical properties of Ti<sub>3</sub>AlC<sub>2-y</sub>N<sub>y</sub>. Ti<sub>3</sub>AlCN (y=1) showed the highest Vickers hardness and flexural strength among the studied samples, reaching 5.54 GPa and 550 MPa, respectively. However, the electrical conductivity and CTEs of Ti<sub>3</sub>AlC<sub>2-y</sub>N<sub>y</sub> solid solutions decreased with increasing N content, from 8.93´10<sup>-6</sup> K<sup>-1</sup> to 7.69 ´10<sup>-6</sup> K<sup>-1</sup>，and 1.33´10<sup>6</sup> S/m to 0.95´10<sup>6</sup> S/m, respectively. This work demonstrates the tunable properties of Ti<sub>3</sub>AlC<sub>2-y</sub>N<sub>y</sub> solid solutions with varying N contents, and also widens the member of MAX phase family for fundamental studies and applications.