Enhanced properties of multi‐element soluted (Nb0.8Ti0.05Zr0.05Mo0.05M0.05)4AlC3 (M = Hf, Ta) ceramics

Abstract Recently multielements solid solution has shown significant improvement to the mechanical properties of parent MAX phases. Therefore, in this work, five elements with different radii were incorporated to check the effect on properties of MAX phases. (Nb 0.8 Ti 0.05 Zr 0.05 Mo 0.05 Hf 0.05 ) 4 AlC 3 (MAX Hf ) and (Nb 0.8 Ti 0.05 Zr 0.05 Mo 0.05 Ta 0.05 ) 4 AlC 3 (MAX Ta ) ceramics were successfully synthesized using the spark plasma sintering technique. The microstructure and elemental map analysis results further confirmed that the five transition metals were successfully solid soluted at the M‐sites of the hexagonal M 4 AlC 3 unit cell. The mean elemental compositions for M‐site elements were achieved as Nb 0.85 Ti 0.052 Zr 0.035 Mo 0.027 Hf 0.036 and Nb 0.847 Ti 0.051 Zr 0.043 Mo 0.025 Ta 0.033 for MAX Hf and MAX Ta ceramics, respectively. The electrical and thermal conductivities of multielement solid solution MAX phases were decreased compared to pure Nb 4 AlC 3 . However, Mechanical properties were significantly increased with the solid solution of five transition metals. The fracture toughness, flexural strength, compressive strength and Vickers hardness (10 N) of MAX Hf and MAX Ta ceramics were achieved as 8.87 MPa m 1/2 , 448 MPa, 867 MPa, 6.5 GPa and 10.36 MPa m 1/2 , 557 MPa, 1039 MPa, 8.2 GPa, respectively. The enhanced mechanical properties suggest the effectiveness of the solid solution strengthening effect and provide new opportunities to further tailor the mechanical properties of the MAX phase ceramics.