Microstructure and mechanical properties of pulsed electric current sintered B4C–TiB2 composites

▶ Fast densification of B4C–TiB2 particulate composites. ▶ Oxide impurity removal by evaporation. ▶ Judiciously controlled loading cycle during pulsed electric current sintering. ▶ High strength micrometer sized B4C–TiB2 composites. Monolithic B4C, TiB2 and B4C–TiB2 particulate composites were consolidated without sintering additives by means of pulsed electric current sintering in vacuum. Sintering studies on B4C–TiB2 composites were carried out to reveal the influence of the pressure loading cycle during pulsed electrical current sintering (PECS) on the removal of oxide impurities, i.e. boron oxide and titanium oxide, hereby influencing the densification behavior as well as microstructure evolvement. The critical temperature to evaporate the boron oxide impurities was determined to be 2000°C. Fully dense B4C–TiB2 composites were achieved by PECS for 4min at 2000°C when applying the maximum external pressure of 60MPa after volatilization of the oxide impurities, whereas a relative density of 95–97% was obtained when applying the external pressure below 2000°C. Microstructural analysis showed that B4C and TiB2 grain growth was substantially suppressed due to the pinning effect of the secondary phase and the rapid sintering cycle, resulting in micrometer sized and homogeneous microstructures. Excellent properties were obtained for the 60vol% TiB2 composite, combining a Vickers hardness of 29GPa, a fracture toughness of 4.5MPam1/2 and a flexural strength of 867MPa, as well as electrical conductivity of 3.39E+6S/m.