Sintering Mechanism of Pure B4C Ceramic Prepared by Hot Oscillating Pressing and with Excellent Mechanical Properties

Pure boron carbide (B4C) ceramics are sintered by hot oscillating pressing at temperatures of 1700-1900 degrees C for different soaking times. The densification mechanism, grain growth kinetics, and mechanical properties obtained under these sintering conditions are systematically investigated. It is found that the fully densified B4C ceramic is obtained at 1900 degrees C within 120 min, possessing an excellent combination of hardness (approximate to 38.5 GPa) and fracture toughness (4.8 MPa m(1/2)). The densification mechanisms during sintering are as follows: viscous flow at the initial stage (relative density D ranged from 55% to 65%) under 1700 degrees C; lattice diffusion/grain boundary diffusion at the sintering stage (62% < <D< 75%) of 1800 and 1850 degrees C; grain boundary sliding by dislocation motion at the late stage (65%<D< 82%) of 1700 degrees C and the sintering stage(75% < D < 90%) at 1800-1900 degrees C; and dislocation gliding and stacking faults at the final stage (90%< D < 95%) occurring at 1850-1900 degrees C. The dislocation motion exhibits a critical impact on the densification process of the hot oscil-lating-pressed B4C ceramic. The grain growth kinetics at 1900 degrees C is controlled bygrain boundary diffusion