Abstract: The poor sinterability of B4C limits its widespread application because both high temperature and high pressure are required for a complete densification. Moreover,B4C suffers from a low strength and fracture toughness,but possesses a high potential use in hiqh temperature region because of its superb hardness and corrosion resistance. Hot press reaction sintering of B4C-Si-WC/TiC-Co mixtures results in B₄C-TiB₂-W₂B₅ composite with a high density and much improved mechanical properties. The iufluence of hot isostatic pressing(HIP)on the im-provement of mechanical properties is also investigated and related to the strengthening and toughening mechanisms. In comparison to single phase B4C ceramics,bending strength is im-proved to 1030MPa(HIP),K(IC) to 5. 6MP3·,hardness is comparable with HV=38GPa,and of practical importance, sintering temperature is lowered to 1700～1800℃.

Key words: Boron carbides, chemical reactions-sintering, mechanical properties