Synergistic enhancement of strength and ductility of Ti2AlC/TiAl through Mn solid solution and interface manipulation

Introducing Ti2AlC particles into TiAl alloys can effectively improve their strength, but this can also lead to stress concentration at the interface, resulting in the reduction of ductility. Therefore, Mn is adopted to synergistically improve the strength and ductility of the Ti2AlC/TiAl composite through solid solution and interface manipulation. The first-principles calculation shows the Ti-Mn bonds are formed at the Ti2AlC/TiAl interface after Mn doping, characterized primarily by metallic bonds with some covalent bonding. This combination preserves strength while enhancing ductility. Then, Ti2AlC/TiAl-Mn composite is prepared. The Ti2AlC, with an average size of 1.6 μm, is uniformly distributed within the TiAl matrix. Mn doping reduces the lamellar colony size and lamellar thickness by 25.1% and 26.3%, respectively. And a small quantity of Mn accumulates at the boundaries of the lamellar colonies. The Mn content must be controlled to avoid segregation, which may negatively impact performance. The yield stress, ultimate compressive stress, fracture strain, and product of strength and plasticity of the Ti2AlC/TiAl-Mn composite have been increased by 5.5%, 11.5%, 10.4%, and 23.0%, respectively, compared to those of the Ti2AlC/TiAl composite. The enhancement in strength is due to the combined effects of grain refinement, solid solution of Mn, and twining strengthening. Grain refinement and twin strengthening also can reduce stress concentration and improve ductility. In addition, at the electronic level, the Ti-Mn bond formed at the interface is contributed to the improvement of ductility.