Abstract:

Dense B₄C ceramic matrix composites were synthesized by reactive hot press sintering at the temperature of 1800℃ and the pressure of 35 MPa using commercial available B₂O₃, Al, graphite, and B₄C as raw materials. Microstructure, phase composition and mechanical properties were observed and tested. The composite ceramics were penetrated by a 7.62 mm calibre armor-piercing bullet at restrained and unrestrained states. Then the protection factor was calculated according to the rules of DOP method. In comparison, the ballistic performances of AZ ceramic and monolithic B₄C were also investigated. The results indicated that the main phase of the as-prepared sample was B₄C (~70wt%) and the secondary phase was Al₂O₃. A complex intermediate phase contained Al-B-O was found filled in the holes between the main phase and the secondary phase. Density, hardness, bending strength and fracture toughness of the composite were 2.82 g/cm³, 41.5 GPa, 380 Mpa, and 3.9 MPa•m^1/2, respectively. The fracture toughness significantly increased by 85.7s% as compared with that of the pure B₄C (2.1 MPa•m^1/2). The protection factor of the composite ceramic gets 11% and 70% increase compared to those of AZ ceramic and monolithic B₄C, respectively. At restrained states, the protection factors of all the samples are further improved by about 10%. These results suggested that B₄C/Al₂O₃ composite ceramic prepared by reactive hot press sintering method might be a good ceramic armor material.

Key words: B₄C, composite ceramic, mechanic property, restrained state, protection factor