Multi-stage spark plasma sintering to study the densifi cation mechanisms of boron carbide

The densification kinetics of boron carbide (B4C) during multi-stage spark plasma sintering was studied. The densification mechanisms were analyzed according to the stress exponent n and the apparent activation energy Qd using a creep deformation model. The results showed that the densification mechanisms were controlled by viscous flow and grain boundary diffusion at the low effective stress with initial temperature range of 1600-2000 degrees C, while the dominant mechanism is the dislocation climb at the effective stress regime with final temperature of 2100 degrees C and the multi-stage sintering can reduce the apparent activation energy. Meanwhile, the scheme of multi-stage sintering can obtain nearly theoretical dense B4C and avoid grain growth. Therefore, the basic mechanical properties suggesting a good combination of high hardness (37.63GPa) and bending strength (539.86 MPa) was obtained by the multi-stage sintering.