High-entropy M2AlC-MC (M=Ti, Zr, Hf, Nb, Ta) composite: Synthesis and microstructures

A high-entropy M2AlC-MC (M=Ti, Zr, Hf, Nb, Ta) composite was produced by reactive hot pressing using Ti, Zr, Hf, Nb, Ta, Al, and graphite as raw materials. Successful solution of the five transition metals in both hexagonal M2AlC and cubic MC was confirmed by XRD, SEM, atom-resolved STEM and EDS elemental analyses. The high-entropy M2AlC shows larger delocalization of atoms and higher lattice strain than the high-entropy MC along with considerable amount of Al vacancies. The formation mechanism of the high-entropy composite has been discussed. The Vickers hardness of the composite is measured to be 11.1 ± 1.1 GPa.