The creep behavior of (TiB + TiC+Y2O3)/alpha-Ti composites at high temperature and short-term

In present study, the creep behavior of (TiB + TiC+Y2O3)/alpha-Ti composite with C-1 and C-2 microstructure were investigated with applied stress of 200 MPa and at 650-700 degrees C. The steady state creep rate increased by an order of magnitude from 650 degrees C to 700 degrees C, and the C-2 microstructure shown worse creep performance compared to C-1 microstructure. The creep activation energy of C-1 and C-2 microstructure were 359.5 kJ/mol and 380.2 kJ/ mol, respectively, which were higher than the lattice diffusion in alpha-Ti. And the less QG due to coarse micro-structure was responsible for its higher creep activation energy in C-2. In addition to cracks were observed at beta grain boundary, alpha colony boundary, alpha/beta phase boundary, they were also observed near the fracture TiB whiskers and near decohesion reinforcements. The cracks in C-2 were mainly concentrated near the reinforcement, while those in C-1 were mainly concentrated in the matrix part. Further analysis confirmed that the creep deformation mechanism of C-2 microstructure was controlled by reinforcements, but the creep deformation mechanism of C-1 microstructure was controlled by matrix microstructure. Summarily, the effect of reinforcement on creep deformation of (TiB + TiC+Y2O3)/alpha-Ti composite could be divided in two aspect: microstructure influence and the reinforcement itself. For reinforcement itself, it indeed affected the dislocation movement and creep fracture behavior, and then improved the creep performance. However, for microstructure influence, the fine grain (more grain boundary), coarsen microstructure (more equiaxed characteristics of alpha lamellar) caused more grain boundary slip to participate in creep deformation, which in turn deteriorated creep performance. In this study, the latter effect was somewhat bigger.