Study On Synthesis And Mechanical Properties Of Ti₃SiC₂ By Reactive Sintering

Ti₃SiC₂ (Titanium silicon carbide) brings on the attraction of people largely owing to its excellent properties. Ti₃SiC₂ combines the properties of both metals and ceramics. Like metals, it is a good thermal and electrical conductor, relatively soft, higher elastic modulus. Like ceramics, it is higher yield strength and exhibits excellent high temperature mechanical properties. It is resistant to thermal shock and unusually damage, and exhibits excellent corrosion resistance. Except for above properties, unlike conventional ceramics, the Ti₃SiC₂ can be machined by conventional tools without lubricant, which is of great technological importance for their application. Additionally, Ti₃SiC₂ has the capability of self-lubrication with an ultra-low friction coefficient. These excellent properties mentioned above make it become another important material. To date, many methods have been used to synthesize Ti₃SiC₂, such as chemical-vapor deposit (CVD), hat pressing (HP), self-propagating high temperature reaction synthesis (SHS), solid-liquid reaction sintering, spark plasma sintering (SPS), hot-isostatic pressing (HIP) and so on. Unfortunately, it is difficult for Ti₃SiC₂ to be synthesized as a pure phase, being often accompanied by unacceptably large amounts of TiC, SiC and silicides. This is unfavourable for properties of synthesized Ti₃SiC₂. The technology is sophisticated to synthesize Ti₃SiC₂, so the final cost for synthesizing Ti₃SiC₂ is very high, and the energy consumption for synthesizing Ti₃SiC₂ will be excessive.The reaction sintering method was used to prepare single-phase Ti₃SiC₂ from Ti/Si/C, Ti/SiC/C, TiC/Si/Ti mixed powers. The effects of sinter parameters Ti₃SiC₂ on the purity and porosity of sintered Ti₃SiC₂ were studied in this work, such as sintering temperature, content of Si in molar ratio, sintering time. The results shown that the bulk Ti₃SiC₂ ceramic which the amount of Ti₃SiC₂ is over 93wt% could been obtained successfully by reaction sintering used 3Ti/1.2Si/2C ratio mixture powders when the sintering temperature was 1250℃and the sintering time was 1 hour. The sintering temperature is so far the lowest for synthesizing Ti₃SiC₂.According to the experimental results, the binary phase diagram of Ti-Si, microstructure of Ti₃SiC₂ and TiC as well as thermodynamic data, the reaction mechanism of reaction-sintered Ti₃SiC₂ would be analyzed. The results showed that the reaction mechanism for synthesizing Ti₃SiC₂ is solid-liquid reaction. With the sintering temperature increases, the Ti atom reacts with the C atom and Si atom to form TiC and Ti₅Si₃, respectively. Then, the Ti₅Si₃ reacts with Ti to form Ti-Si liquid phase around it. At last, the TiC reacts with Ti-Si liquid phase to form Ti₃SiC₂. However, the excessively higher sintering temperature will make the Ti₃SiC₂ to decompose the TiC and gaseous Si.The hardness and the flexural strength of Ti₃SiC₂ which was sintered at 1250℃were tested as HB101 and 105.59MPa, respectively. The fracture damage mechanism of Ti₃SiC₂ is dominated by the grain boundary and pore fracture through the observations and analysis of fractograph. At the same time, the fracture damage of Ti₃SiC₂ can be prevented from the energy consumption forms, such as intragranular fracture, delamination, cracks deflection in grains, micro-cracks propagation and grains evulsions, and so on. This indicates that the Ti₃SiC₂ possesses the quasi-plasticity...