High-Strength B4C-TaB2 Eutectic Composites Obtained via In Situ by Spark Plasma Sintering

The in situ synthesis/consolidation of B4C-TaB2 eutectic composites by spark plasma sintering ( SPS) is reported. Samples for the evaluation of bending strength were cut from specimens with diameters of 30 mm. The sample prepared for the three-point flexural strength test had fibers of tantalum diboride with diameter of 1.3 +/- 0.4 mu m distributed in the B4C matrix, thereby reducing composites brittleness and yielding an indentation fracture toughness of up to 4.5 MPa.m(1/2). Furthermore, the Vickers hardness of B4C-TaB2 eutectics formed by SPS was as high as 26 GPa at an indentation load of 9.8 N. The flexural strength of the B4C-TaB2 system has been reported for the first time. Some steps were identified in the load-displacement curve, suggesting that micro-and macrocracking occurred during the flexural test. Ceramic composites with a eutectic structure exhibited a room-temperature strength of 430 +/- 25 MPa. Compared with other eutectic composites of boron carbide with transition-metal diborides, room-temperature strength the B4C-TaB2 was 40% higher than that of B4C-TiB2 ceramics, demonstrating advantage of the in situ synthesis/consolidation of eutectic composites by SPS.