Microstructure and mechanical properties of investment casted titanium matrix composites with B4C additions

Titanium matrix composites (TMCs) are prepared by investment casting in a vacuum consumable kish furnace. The effects of B4C additions on the microstructures and tensile properties of TMCs are investigated. With the addition of B4C, the microstructure of TMCs is refined and the strength is improved. The yield strength of TMCs is evaluated by a comprehensive model that combines the strengthening effects of TiB whiskers/TiC particles, grain refinement and solution strengthening of the matrix, which is consistent with the experimental results in the current study. It is found that the yield strength enhancement of TMCs is mainly due to grain refinement and solution strengthening. During tensile deformation, the dislocation piles up at the interface between TiB whisker and matrix, which allows the TiB whiskers to bear extra load and therefore enhances the strength of TMCs. The plastic deformation is localized due to the action of TiB whiskers and this results in the brittle fracture of TMCs.