Synthesis and enhanced mechanical properties of compositionally complex MAX phases

A novel strategy of fabricating compositionally complex MAX phases was successfully developed. Multicomponent 413 MAX phase solid solutions (Ti_0.36Nb_0.27Ta_0.37)₄AlC_2.8 and (Ti_0.28Nb_0.26Ta_0.28V_0.18)₄AlC_2.9 simultaneously containing 3 and 4 transition-metal elements at M site were experimentally synthesized via hot pressing equimolar mixture of 211 type MAX phase powders. By elemental analysis and structural characterization, it can be verified that those uniform compositionally complex solid solutions can be obtained only in the presence of Cr₂AlC in raw powders. Those compositionally complex MAX phase solid solutions exhibit typical layered structures with distinct elongated grains. This discovery further enriches the MAX phases family and provide a new avenue for tailoring the properties of these materials. MAX phase composites containing around 87.5 vol.% (Ti_0.36Nb_0.27Ta_0.37)₄AlC_2.8 exhibit a high flexural strength of 720 MPa and a high fracture toughness of 9.5 MPa m^0.5.