Ti₂Al(C, N) Solid Solution Reinforcing TiAl-Based Composites: Evolution of a Core-Shell Structure, Interfaces, and Mechanical Properties

In this work, Ti₂Al(C, N) solid solution with lamellar structure-enhanced TiAl matrix composites was synthesized by vacuum arc melting, using bulk g-C₃N₄, Ti, and Al powders as raw materials. The phases, microstructures, interfaces, and mechanical properties were investigated. MAX phase of Ti₂Al(C, N) solid solution with lamellar structure was formed. During the melting process, first, C₃N₄ reacted with Ti to form Ti(C, N) by Ti + C₃N₄ → Ti(C, N). Then Ti₂Al(C, N) was formed by a peritectic reaction of TiAl(l) + Ti(C, N)(s) → Ti₂Al(C, N). C₃N₄ is the single reactant that provides C and N simultaneously to final product of Ti₂Al(C, N). The interfaces of TiAl//Ti₂Al(C, N) and Ti₂Al(C, N)//Ti(C, N) display perfect orientation relationships with low misfit values. The microhardness, compressive strength, and strain of best-performing TiAl-10 mol % Ti₂Al(C, N) composite were improved by 45%, 55.7%, and 50% compared with the TiAl alloy, respectively. Uniformly distributed Ti₂Al(C, N) and unreacted Ti(C, N) particles contributed to the grain refinement and reinforcement of the TiAl matrix. Laminated tearing, particle pull-out, and the crack-arresting of Ti₂Al(C, N) are crucial for the improvement in compressive strength and plasticity of the composites.