Densification kinetics of boron carbide with medium entropy alloy as a sintering aid during spark plasma sintering

Abstract The high sintering temperature of pure B ₄ C considerably limits its widespread application, thus searching an effective sintering aid is critical. In this work, B ₄ C‐based ceramic with 1 vol.% nonequiatomic Fe ₅₀ Mn ₃₀ Co ₁₀ Cr ₁₀ medium entropy alloy as a sintering aid were fabricated at 1900‐2000°C by spark plasma sintering (SPS) under applied pressure, and their mechanical properties were examined and compared with pure B ₄ C ceramic sintered at same condition. The maximal flexural strength of 255.59 MPa, microhardness of 2297.6 Hv _0.2 and fracture toughness of 3.62 MP a m ^1/2 could be obtained at optimized SPS pressure of 50 MP a, which were all higher than those of pure B ₄ C ceramic. To better understand the densification kinetics mechanisms, the densification ratio as a function of SPS temperature and pressure was theoretically analyzed using steady creep model. It was found that densification controlled by grain‐boundary sliding at lower pressure transferred to power law creep regime at higher pressure, which were proved by the dislocation net shown in transmission electron microscopy image.