Synthesis and characterization of high entropy carbide-MAX two-phase composites

Abstract

In the present work, the formation of high entropy MAX phase during mechanical alloying and subsequent spark plasma sintering (SPS) of two powder mixtures with (HfZrNbTiTa)3SiC2 and (HfZrNbTiTa)3(SiAl)1.1C1.95 stoichiometries is investigated. The results indicate that a high entropy carbide (HEC) with cubic HfC-prototype structure is formed for both compositions after 7 h of mechanical alloying. The microstructural observations indicate the nano-sized nature of the as-milled powders. For both specimens, consolidation at high temperatures leads to a phase transition from single HEC to HEC-MAX complex. Ultrahigh microhardness values of 11 ± 2 GPa and 8 ± 2 GPa were obtained for the consolidated (HfZrNbTiTa)3SiC2 and (HfZrNbTiTa)3(SiAl)1.1C1.95 specimens, respectively. The results also revealed that the (HfZrNbTiTa)3(SiAl)1.1C1.95 exhibits ferromagnetic behavior with low magnetization saturation of only 1.709 emu/g, while (HfZrNbTiTa)3SiC2 shows a ferromagnetic behavior with relatively low coercivity and magnetization saturation. Finally, the findings provide a new route to tailor mechanical properties of HEC-MAX complexes by controlling the evolution of MAX phase.