Pressureless densification and properties of high-entropy boride ceramics with B4C additions

•Fully dense high entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2 ceramics (HEB) via solid pressureless sintering was achieved at 1900℃, 200-300℃ lower than that reported in the literature.•Mechanical properties of as-obtained HEB ceramics consolidated by pressureless sintering are comparable or even higher than those of counterparts sintered under pressure.•The melting point of HEB was first calculated and it reveals that the melting point of HEB (3359℃) is only a little lower than that of HfB2 (3380℃), while using B4C as sintering aids, there is a broad temperature window for pressureless sintering of HEB.