Formation kinetics of multi-component carbide matrix via reactive melt infiltration

Multi-component carbide ceramics (MCC) serve as a crucial matrix in developing ultrahigh temperature ceramic matrix composites. Research on their formation during reactive melt infiltration (RMI) offers valuable insights into both the structural evolution and mechanisms at play. By reacting HfSi₂–ZrSi₂–TiSi₂ mixed alloys with graphite, there are distinct phase formations at different temperature regimes. At lower temperatures, the interaction between the alloy mixture and graphite forms a three-layer structure: an outermost layer of HfC, a middle layer of (ZrTi)C, and an innermost layer of SiC. This stratification arises due to the differing melting points and reactivity of the alloy components. In contrast, at elevated temperatures, significant interdiffusion among the different carbides occurs, resulting in the formation of a single-phase solid solution. This leads to a double-layer structure with an outer homogeneous (HfZrTi)C layer and an inner layer of SiC. Kinetics analysis demonstrates that silicon from the molten alloys continuously diffuses toward the graphite, forming the SiC layer, while carbon diffuses outward through the existing SiC layer, reacting with the alloy to yield Zr-, Ti-, and Hf-carbides through precipitation. Carbon fiber reinforced MCC composites were prepared using RMI with the same alloy. The consistent morphology observed in the matrix of these composites confirms the formation mechanism during the RMI process. The resulting composites exhibited excellent mechanical strength.