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

Abstract

The in situ synthesis/consolidation of B 4 C-TaB 2 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 threepoint flexural strength test had fibers of tantalum diboride with diameter of 1.3 AE 0.4 lm distributed in the B 4 C matrix, thereby reducing composites brittleness and yielding an indentation fracture toughness of up to 4.5 MPaÁm 1/2 . Furthermore, the Vickers hardness of B 4 C-TaB 2 eutectics formed by SPS was as high as 26 GPa at an indentation load of 9.8 N. The flexural strength of the B 4 C-TaB 2 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 AE 25 MPa. Compared with other eutectic composites of boron carbide with transition-metal diborides, room-temperature strength the B 4 C-TaB 2 was 40% higher than that of B 4 C-TiB 2 ceramics, demonstrating advantage of the in situ synthesis/consolidation of eutectic composites by SPS.

High‐temperature strength and plastic deformation behavior of niobium diboride consolidated by spark plasma sintering

“…Although plastic deformation appears to control the fracture at 1800°C, the specimen has an elastic end to the load–displacement curve starting at a stress of 373 MPa. This has some nonlinear deviations, which in eutectic composites suggests the formation of micro‐ and macrocracks during fracture, which can be observed during the fracture of layered materials . However, in the present study, this is an indication of fatigue‐like creep‐induced fracture, which occurred during plastic deformation and was caused by some grains are being separated at specific crystallographic orientation.…”

Fracture and property relationships in the double diboride ceramic composites by spark plasma sintering of TiB2 and NbB2

“…Here one may observe the appearance of NbB 2 subgrains which fracture in a different manner when compared to Figure G,I. At 1200°C (Figure D), these subgrains have a needle‐like shape, that is similar to a fracture of the eutectic B 4 C–NbB 2 or B 4 C–TaB 2 ceramic composites at HT. Some of these needle‐shaped grains appeared at 1200°C, coinciding with strength increase in for DDCCs.…”

Synthesis, densification, and microstructure of TaC‐TaB2‐SiC ceramics

“…Mechanical properties of these samples are listed in Table . Young's modulus decreases from 556 to 498 GPa with the addition of more (B 4 C, Si), since TaC (567 GPa) has a higher inherent Young's modulus than TaB 2 (560 GPa) and SiC (460 GPa) . Fracture toughness of TaC‐TaB 2 ‐SiC ceramics ranges from 3.26 to 3.59 MPa∙m 1/2 , which is comparable with TaC ceramics (3.5 MPa∙m 1/2 ) and TaC‐TaB 2 ceramics (3.4 MPa∙m 1/2 ) .…”

“…Young's modulus decreases from 556 to 498 GPa with the addition of more (B 4 C, Si), since TaC (567 GPa) has a higher inherent Young's modulus than TaB 2 (560 GPa) and SiC (460 GPa). [23][24][25] Fracture toughness of TaC-TaB 2 -SiC ceramics ranges from 3.26 to 3.59 MPa•m 1/2 , which is comparable with TaC ceramics (3.5 MPa•m 1/2 ) and TaC-TaB 2 ceramics (3.4 MPa•m 1/2 ). 8 Generally, fracture toughness varies little with composition, as seen from Table 2, and the TBS-15 sample exhibits better fracture toughness than the other samples.…”