Study of effect of Mn addition on the mechanical properties of Ti2AlC/TiAl composites through first principles study and experimental investigation

The effect of Mn on the mechanical properties of the Ti2AlC/TiAl composites is investigated by experiments and first principles calculations. The Mn atoms preferentially occupy the Al sublattice sites and can cause the lattice contraction of TiAl along its c-axes. As a result, the lattice tetragonality of TiAl, which is related with its intrinsic brittleness, could be reduced. The calculation results are consistent with the experimental observations. The addition of Mn remarkably improves the ductility of the composites. Moreover, the strength and work-hardening rate are also enhanced due to the solid solution of Mn and the grain refinement of the TiAl matrix. The strength and the work-hardening rate increase with the increase in the Mn content, while the ductility increases firstly and then decreases. The composite with the addition of 2 at.% Mn possesses the best compression properties, of which the average compression strength is 256 MPa higher than that of Mn-free sample, and the average compression fracture strain increases from 16.4% to 19.9%.