Abstract ZrB2 matrix composites toughened with in-situ formed ZrC were fabricated by spark plasma sintering (SPS) utilizing ZrB2/ZrO2/graphite powder mixtures at 1900 °C for 7 min under 40 MPa load. Different amounts of graphite nano-flakes (3, 6, and 9 wt%) were added to ZrB2–20 vol% ZrO2 aiming in-situ formation of ZrC reinforcement. Clean ZrB2/ZrC interfaces were observed in the as-sintered microstructure, especially in the composite containing 6 wt% graphite. The reduction of ZrO2 with graphite, which formed ZrC, was progressed over a zirconium oxycarbide (ZrCxOy) intermediate. The hardness of the SPSed ZrB2-based composites was decreased with increasing the graphite content. However, the fracture toughness of the composites showed a reverse trend. By adjusting the graphite content to 6 wt%, excellent control of microstructure could be achieved for the prepared composites with a higher amount of ZrC and lower content of other unfavorable phases. It was finally found that achieving the optimum microstructure of the composite could improve its mechanical performance, and provides a hardness of 17.3 GPa and fracture toughness of 5.0 MPa.m1/2.

中文翻译：

---

用 ZrO2 和石墨前体原位合成 ZrC 增韧 ZrB2 基复合材料

摘要 采用放电等离子烧结 (SPS)，采用 ZrB2/ZrO2/石墨粉末混合物，在 1900 °C 和 40 MPa 载荷下持续 7 min，制备了用原位形成的 ZrC 增韧的 ZrB2 基复合材料。将不同数量的石墨纳米薄片（3、6 和 9 wt%）添加到 ZrB2–20 vol% ZrO2 中，旨在原位形成 ZrC 增强材料。在烧结态微观结构中观察到清洁的 ZrB2/ZrC 界面，尤其是在含有 6 wt% 石墨的复合材料中。ZrO2 与石墨的还原形成 ZrC，是在碳氧化锆 (ZrCxOy) 中间体上进行的。SPSed ZrB2 基复合材料的硬度随着石墨含量的增加而降低。然而，复合材料的断裂韧性却呈现出相反的趋势。通过将石墨含量调整为 6 wt%，制备的复合材料具有较高的 ZrC 含量和较低的其他不利相含量，可以实现对微观结构的出色控制。最终发现，实现复合材料的最佳微观结构可以提高其力学性能，并提供 17.3 GPa 的硬度和 5.0 MPa.m1/2 的断裂韧性。