Mechanism-driven strengthening of MAX phase ceramics by Ti <sub>3</sub>C <sub>2</sub>T <sub> <i>x</i> </sub> MXene: A comparative study on Cr <sub>2</sub>AlC and Ta <sub>2</sub>AlC
Lu Liu, Mutian Zhang, Qifeng Zhuang, Xiyu Xiao, Cong Hu, Chenrui Qian, Shijie Pan, Yue He, Jiajia Wang, Guobing Ying
Abstract
MAX-phase ceramics combine metallic and ceramic characteristics, while their two-dimensional derivatives, MXenes, have shown great potential as reinforcements for high-temperature structural applications. Leveraging the structural similarity between MXenes and their MAX-phase precursors, Ti<sub>3</sub>C<sub>2</sub>T<em><sub>x</sub></em> was incorporated into two 211-type MAX ceramics, Cr<sub>2</sub>AlC and Ta<sub>2</sub>AlC, to investigate its effects on mechanical properties and strengthening mechanisms.<strong> </strong>The addition of MXene improved both flexural strength and fracture toughness. The optimal enhancement was observed at 2 wt.% for Cr<sub>2</sub>AlC (22% strength increase) and 4 wt.% for Ta<sub>2</sub>AlC (33% strength increase). Microstructural analysis revealed partial solid solution and TiC<em><sub>y</sub></em> formation in Cr<sub>2</sub>AlC, while Ta<sub>2</sub>AlC exhibited complete solid solution behavior. DFT calculations confirmed that Ti ion diffusion into Ta<sub>2</sub>AlC is energetically more favorable due to weaker Ta–Al bonding and larger interlayer spacing.<strong> </strong>A multi-mechanism Δ<em>σ</em> model was used to decouple the strengthening contributions from solid solution, grain refinement, dislocation density, and load transfer. In Cr<sub>2</sub>AlC, grain refinement and second-phase strengthening dominated, whereas in Ta<sub>2</sub>AlC, solid solution and grain refinement prevailed. Theoretical predictions matched well with experimental data after incorporating a correction term into the shear-lag model. These findings provide insights into MXene-induced strengthening in layered ceramics and offer guidance for designing high-performance, damage-tolerant MAX-phase materials.