Investigation On The Synthesis And Performance Of TiC Particulates Reinforced TiAl Intermetallic Matrix Composites

TiAl(γ) intermetallic has excellent potential to become one of the most important aerospace materials because of its high refractory nature, low densities, high specific strength, high melting temperature, and environmental resistance at elevated temperature. But the brittleness of room temperature and low strength at high temperature has been greatly preventing its practical use. TiAl intermetallic matrix composites reinforced with ceramic particles is an effective method to overcome the above limitations. In this dissertation, TiAl intermetallic powders were firstly synthesized, then added TiC particles to it and fabricated TiC/TiAl composites using the technology of spark plasma sintering (SPS), which was used to attain the purpose of enhancing the strength and improving fracture toughness of TiAl matrix.TiAl intermetallic powders fabricated by the rapid heating method on the basis of combustion synthesis techniques. The effect of processing parameters on preheating temperature and holding time to the fabrication of TiAl powders were researched. The experimental results showed that the synthesis of TiAl intermetallics can be achieved by these two powders without pre-molding and the reaction of elemental Ti, Al is diffusion controlled, including intermediate steps in which TiAl3 and Ti3Al phases form. The resultant from the reaction consists mainly of TiAl and less Ti3Al phase. Raising the reaction temperature and prolonging the time at high temperatures are helpful to the procedure of reaction and the synthesis of TiAl intermetallics.Using SPS techniques, TiC/TiAl composites was fabricated. The experimental results showed that the sintering mainly happened at the course of heating-up period, and the changing trend of heating-up and shrinkage curve of TiAl and TiC/TiAl composites is consistent. TiC/TiAl composites possessed microstructure with following characterization: (1) micron TiC particles dispersed assembled on the matrix. (2) The microstructure of matrix was interveined the two phase (γ+α2).The experimental results show that the composite includes TiAl, Ti3Al, TiC phases. TiC/TiAl composites possessed good mechanical properties. Both flexural strength and fracture toughness increases at first and then declines with TiC content and reached a maximum value at 10wt%TiC and 5wt%TiC, respectively. Moreover, TiC/TiAl composites have higher hardness than unreinforced TiAl matrix.