Synthesis And Properties Of Ti₅Si₃Matrix In-situ Composites

This research mainly based on the preparation of new type materials for aeroengine.According to the principle of in-situ synthesis, Ti₅Si₃intermetallic and graphite dopingTi₃SiC₂/Ti₅Si₃in-situ composites were prepared by in situ method by vacuum hot pressingtechnique. The reactive Gibbs free energies, the reactive formation enthalpies and adiabatictemperatures concerning the preparation of in situ composites using elemental powders of Ti,C and Si have been investigated. Then a systematic discussion of the objective certainty andpractical feasibility were given.The X-ray diffraction and energy analysis were investigated to analyze the phases of Ti₅Si₃intermetallic and Ti₃SiC₂/Ti₅Si₃in-situ composites and they are prepared by vacuum hotpressing technique using elemental powders of Ti and Si. The matrix phase intermetalliccompound Ti₅Si₃and ceramic strengthening phase Ti₃SiC₂are mainly contained in theproduct.The results of analysis of the mechanical properties of material showed that, the fracturetoughness, flexural strength, compressive strength of the doped graphite1.61wt%Ti₃SiC₂/Ti₅Si₃composites are increased by63.7%,59%and82%more than the single-phaseTi₅Si₃. The surface morphology analysis and port morphology of Ti₅Si₃and graphite dopingTi₃SiC₂/Ti₅Si₃in-situ composites were observed by scanning electron microscopy（SEM）,analysis of the graphite doping Ti₃SiC₂/Ti₅Si₃in situ composites strengthening andtoughening mechanism were studied. Preparation of Ti₅Si₃and Ti₃SiC₂/Ti₅Si₃compositesdensity reached above95%.High temperature oxidation experimental data showed that, the preparation of Ti₅Si₃intermetallic and Ti₃SiC₂/Ti₅Si₃in situ composites oxide were controlled by atomic diffusion,and the Ti₅Si₃intermetallic and Graphite Doping in situ composites content of less than1.61wt%Ti₃SiC₂/Ti₅Si₃in situ composites oxidation resistance at high temperatureconformed to cubic law, graphite doping in situ composites content for the2.52wt%Ti₃SiC₂/Ti₅Si₃composites were in line with the parabolic law. During high temperatureoxidation, Double antioxidative protective layers were formed in single-phase Ti₅Si₃andTi₃SiC₂/Ti₅Si₃composites, which are the outer layer TiO₂and the intermediate layer SiO₂.