Three types of SiC fibers with different tensile strength were employed to prepare unidirectional titanium matrix composites. The strengths of the original SiC fibers and extracted fibers from the composites were measured. The results show that the mechanical properties of fibers are greatly damaged by the consolidation processing of the composite. The strength data of the extracted fibers are used to predict the strength of the composites according to two theoretic models. The Globe Load-Sharing(GLS) model overestimates the strength of the composites. If the Local Load-Sharing(LLS) model assumes that failure occurs after the formation of a cluster with three broken fibers, the model can predict the strength of the composites exactly.
The finite element method based on the equivalent domain integral technique was developed to simulate the push out test and evaluate the interfacial fracture toughness of SiC reinforced titanium matrix composites. A special subroutine was introduced while modeling the push-out test to control interfacial failure process. In addition, the residual stresses, Poisson ratio and friction stresses were all considered in the finite element analysis and the interface debonding was described as a continuous process. The results show that the interfacial fracture toughness of SiC/Timetal-834 is about 50 J/m2. Moreover, the effects of various parameters on the interfacial fracture toughness and the variations of energy release rates at both ends of the specimen were analyzed in detail.
SCS-6 SiC continuous fiber-reinforced Ti-Al intermetallics-matrix composites were fabricated by HIP method and then heat-treated in vacuum under different conditions. The interfacial reaction kinetics and mechanism were studied by using SEM, EDS and XRD. The results show that the content fluctuation of reactive elements such as C, Ti and Si appears in interfacial reaction layers, and multi-layer interfacial reaction compounds form. Alloying element Nb in matrix remarkably diffuses into interfacial reaction zone and changes the activation energy for the interfacial reaction layer growth following a role of parabolic rate. The activation energy (Qk) and (k0) of SCS-6 SiC/super α2 and SCS-6 SiC/Ti2AlNb are 317.664 kJ/mol, 175.709 kJ/mol and 5.4438×10-2 m/s1/2, 1.44×10-5 m/s1/2; respectively, and the diffusion coefficient (DC) is about 10-18—10-20 m2/s. It is confirmed that the SCS-6 SiC/Ti-Al intermetallic composites have higher interface compatibility and stability. Furthermore, compared with SCS-6 SiC/super α2, the interface compatibility and stability of SCS-6 SiC/Ti2AlNb are even higher.
