High‐temperature mechanical behavior of ZrB₂‐based composites with micrometer‐ and nano‐sized SiC particles

Abstract

Using micrometer‐ and nano‐sized SiC particles as reinforcement phase, two ZrB2‐SiC composites with high strength up to 1600°C were prepared using high‐energy ball milling, followed by hot pressing. The composite microstructure comprised finer equiaxed ZrB2 and SiC grains and intergranular amorphous phase. The temperature dependency of flexure strength related to the initial particle size of SiC. In the case of micrometer‐sized SiC, the high‐temperature strength was improved up to 1500°C compared to room‐temperature strength, but the strength degraded at 1600°C, with strength values of 600‐770 MPa. In the case of nano‐sized SiC, the enhanced high‐temperature strength was observed up to 1600°C, with strength values of 680‐840 MPa.

In situ hot‐pressed ZrB2‐based composite with polycarbosilane‐derived SiC: Microstructure and mechanical behavior

“…In addition, the measured grain sizes of ZrB 2 and SiC are ~2.3 μm and ~0.8 μm, respectively. These grain sizes are comparable to those of 20 vol% nanosized SiC‐containing ZrB 2 composite which was prepared using high‐energy ball milling, followed by hot pressing at 1900°C for 1 hour . The smaller ZrB 2 and SiC grains after the sintering are attributable to the homogeneously precipitated nanosized PCS particles in the ZrB 2 slurry and their hindering effect on the grain growth of ZrB 2 during the sintering .…”

“…These grain sizes are comparable to those of 20 vol% nanosized SiC‐containing ZrB 2 composite which was prepared using high‐energy ball milling, followed by hot pressing at 1900°C for 1 hour . The smaller ZrB 2 and SiC grains after the sintering are attributable to the homogeneously precipitated nanosized PCS particles in the ZrB 2 slurry and their hindering effect on the grain growth of ZrB 2 during the sintering . This comparison suggests that ZrB 2 −SiC composite with a homogeneously finer grains microstructure could be obtained using nanosized PCS particles‐containing ZrB 2 mixture powder, followed by hot pressing.…”

“…The corresponding EDS spectrum showed that it contained B, C, O, Mo, Si, and Zr (Figure (D‐3)), and the major composition was Zr and O, thereby it presumably was ZrO 2 . Our earlier study in ZrB 2 ‐20 vol% SiC composites showed that approximately 0.04 wt% ZrO 2 contamination was introduced during the high‐energy ball milling when ZrB 2 ‐20 vol% SiC powder was dry ball‐milled using ZrO 2 media under 300 rpm for 3 hours . Thus, the presence of ZrO 2 may be attributed to few impurities uptake during the ball‐milling procedures for the ZrB 2 −SiC composite investigated in this study, resulted from the abrasion of the ZrO 2 vials and balls during the high‐energy ball milling.…”

“…On the other hand, a recent study of ZrB 2 −SiC−WC composites showed the greatest remained strength at elevated temperature, increasing from 605 MPa at RT to 675 MPa at 1600°C, owing to the removal of the surface oxides from ZrB 2 and SiC powders by reaction with WC during sintering . Very recently, we had prepared the ZrB 2 –SiC and HfB 2 –SiC composites with a homogenously finer microstructure using high‐energy ball milling, followed by hot pressing . The both composites showed improved high‐temperature strength up to 1600°C, compared to the previous works …”

“…Based on previous studies of ZrB 2 –SiC or HfB 2 –SiC composites, two major problems were identified. First, the agglomeration of ultrafine SiC particles in ZrB 2 –SiC mixture powders should be minimized to prevent substantially growth of the SiC grains by fusing together clusters of SiC particles during sintering.…”