Abstract: A series of jet-milling experiments on B₄C coarse powders with specific surface area of 0.52m^2/g and median particle size of 20.4μm were carried out. Effects
of jet-milling times, forming stress and sintering temperature on sintered densities of B₄C were also studied. The results show that powders with particle size of less than 1μm can be
obtained when jet-milled for more than 3 times. The powders jet-milled for 4 times, with specific surface area of 2.53m²/g and median particle size of 0.56μm,
can be pressureless sintered to 78.6% TD at 2200℃and 82.5% TD at 2250℃ for 1h, with average grain size of 28μm and 50μm, comprasive strength of
390MPa and 555MPa respectively.

Key words: boron carbide, ultrafine powder, jet milling, pressureless sintering