The ultra-high sintering temperatures required for high-entropy borides (HEB) pose a significant challenge to their processing and practical application. This study introduces an efficient low-temperature fabrication route for dense HEB-based ceramics using reactive ZrSi₂-assisted heavy direct current sintering, with a maximum heating rate exceeding 3700 °C/min. A porosity of 1.60 ± 0.61% can be achieved at a sintering temperature of 1000 °C, which is reduced by 600-1000 °C compared to state-of-the-art spark plasma sintering/field-assisted sintering techniques processing of HEBs. Microstructural analysis revealed interdiffusion between HEB and ZrSi₂, leading to a core-shell HEB architecture and layered high-entropy silicides. Meanwhile, dislocations and non-uniform stress fields were observed within the HEB grains. These microstructural features synergistically inhibit crack propagation and promote crack deflection and branching. Consequently, both flexural strength and fracture toughness are significantly enhanced. A flexural strength of 963 MPa was attained at 1400 °C, and a fracture toughness of 7.4 MPa·m^1/2 was achieved at 1500 °C, surpassing most reported HEB-based ceramics. These results demonstrate that reactive ZrSi₂-assisted heavy direct current sintering is a profoundly effective approach for low-temperature manufacturing of high-performance HEB-based ceramics.

The preparation of dense ZrB₂-based ceramics typically requires high temperatures and long sintering time, which often result in significant grain coarsening and thus deterioration of mechanical properties. Ultrafast sintering techniques offer a solution to inhibit grain coarsening by reducing the processing time. However, the ultrafast preparation of dense ZrB₂-based ceramics remains a challenge. In this work, we successfully fabricated dense ZrB₂-based ceramics in just a few minutes using heavy continuous direct current (DC) Joule heating and pressing. Notably, the densification rate peaked at 1218 °C, and the densification process was nearly complete at a relatively low temperature of 1500 °C. The application of heavy continuous direct current not only promotes the densification of the ceramics but also enhances the texturization of ZrB₂. This results in optimally aligned ZrB₂ grains that form a three-dimensional bonded skeletal network. These unique microstructures can effectively induce multi-stage fracture surfaces during failure, which helps synergistic strengthening and toughening of the ceramics. The ceramics exhibit remarkable comprehensive mechanical properties, with flexural strength and fracture toughness values reaching 773±114 MPa and 5.88±0.08 MPa·m^1/2, respectively, surpassing those of conventional hot pressed samples. This technique is expected to be applied to other ultra-high temperature ceramics, providing a promising approach for the development of thermal protection materials.