Ti 2 Al(C, N) Solid Solution Reinforcing TiAl-Based Composites: Evolution of a Core-Shell Structure, Interfaces, and Mechanical Properties.

In this work, Ti2 Al(C, N) solid solution with lamellar structure-enhanced TiAl matrix composites was synthesized by vacuum arc melting, using bulk g-C3 N4 , Ti, and Al powders as raw materials. The phases, microstructures, interfaces, and mechanical properties were investigated. MAX phase of Ti2 Al(C, N) solid solution with lamellar structure was formed. During the melting process, first, C3 N4 reacted with Ti to form Ti(C, N) by Ti + C3 N4 → Ti(C, N). Then Ti2 Al(C, N) was formed by a peritectic reaction of TiAl(l) + Ti(C, N)(s) → Ti2 Al(C, N). C3 N4 is the single reactant that provides C and N simultaneously to final product of Ti2 Al(C, N). The interfaces of TiAl//Ti2 Al(C, N) and Ti2 Al(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 % Ti2 Al(C, N) composite were improved by 45%, 55.7%, and 50% compared with the TiAl alloy, respectively. Uniformly distributed Ti2 Al(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 Ti2 Al(C, N) are crucial for the improvement in compressive strength and plasticity of the composites.