The Interfacial Solid State Reactions Of The SiC/Ti-Al Systems

The interfacial solid state reaction between SiC and metals is one of the acute problems, when SiC is used in fabricating for high-temperature structural ceramics and metal matrix composites, etc. In this study, an all-around comprehensive research aimming at SiC/Ti-Al(TiAl,Ti₃Al) plane-interface reaction was done to reveal the phenomena and regularities of the SiC/Ti-Al(TiAl,Ti₃Al) plane-interface solid state reations, which are the essential points during fabricating the SiC reinforced Ti-Al matrix composites and the SiC/Ti-Al alloy high-temprecture components.After the SiC/Ti and SiC/Ti-Al plane-interface couples treating at different temperatures and times, the reaction zones were detected using scanning electron microscope(SEM), energy disperse spectroscopy analyzer(EDS) and X-ray diffraction analyzer (XRD). The studies were mainly focused on the morphologies, the microstructures, and the elemental distributions of the reaction zone. The effects of the heat treatment on them were also studied. Meanwhile, the thermodynamic and kinetic analyses of the SiC/Ti and SiC/Ti-Al interfacial solid state reactions were also carried out.The SiC/Ti interfacial solid state reaction forms Ti₅Si₃C_x and TiC, which are uniformly distributed in the reaction zone. After the SiC/Ti couple was annealed at 1100℃for 5 hours, a continuous single-layer reaction zone of a thickness of about 150μm exits between the SiC terminal and the Ti terminal. The formation of the reaction zone was analyzed in terms of the thermodynamic calculations. And, the model of the SiC/Ti interfacial solid state reaction was also established.The SiC/TiAl interfacial solid state reaction forms TiAl₂, TiC and Ti₅Si₃C_x to construct the reaction zone. After the SiC/TiAl couple was annealed at 1050℃for 10 hours, the reaction zone is about 6um in thickness, which has the microstructure of TiC /(Ti₅Si₃C_x+TiC)/ TiAl₂ (from the SiC terminal to the TiAl terminal). And, the interfacial solid state reaction zone of the SiC/Ti₃Al couple is composed of the phase of Ti₂Al, TiC and Ti₅Si₃C_x. After the SiC/Ti₃Al couple was annealed at 1050℃for 10 hours, the reaction zone is about 8μm in thickness, which has the microstructure of TiC /(Ti₅Si₃C_x+TiC)/ Ti₂Al (from the SiC terminal to Ti₃Al terminal).The formations of the SiC/Ti-Al interfacial solid state reaction zones were analyzed in terms of the thermodynamic calculations. And, the models of the SiC/Ti-Al interfacial solid state reactions were established. During the SiC/Ti-Alinterfacial solid state reactions, TiC and Ti₅Si₃C_x are formed in advace ofTiAl₂(SiC/TiAl) or Ti₂Al(SiC/Ti₃Al). The reactions follow the parabolic growthmechanism, indicating the diffusion controlled reaction kinetics. The kineticfunctions of the SiC/Ti-Al interfacial solid state reactions are as following:The SiC/TiAl system: K=8.47×10^-3exp(-322×10³/RT), m²/sThe SiC/Ti₃Al system: K=1.87×10^-5exp(-259×10³/RT), m²/s.