Mechanism-driven strengthening of MAX phase ceramics by Ti ₃C ₂T _<i>x</i> MXene: A comparative study on Cr ₂AlC and Ta ₂AlC

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, Ti₃C₂T<em>_x</em> was incorporated into two 211-type MAX ceramics, Cr₂AlC and Ta₂AlC, 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 Cr₂AlC (22% strength increase) and 4 wt.% for Ta₂AlC (33% strength increase). Microstructural analysis revealed partial solid solution and TiC<em>_y</em> formation in Cr₂AlC, while Ta₂AlC exhibited complete solid solution behavior. DFT calculations confirmed that Ti ion diffusion into Ta₂AlC 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 Cr₂AlC, grain refinement and second-phase strengthening dominated, whereas in Ta₂AlC, 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.