Growth mechanism of in situ synthesized TiBw in titanium matrix composites prepared by common casting technique

Titanium matrix composites reinforced with TiB and RE2O3 (RE = rare earth metal) were fabricated by a non-consumable arc-melting technology utilizing chemical reaction between titanium, B2O3 and RE. Microstructural characterization of in situ synthesized TiB was performed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). When the volume percentage is relatively low, the TiB shows a typical fine needle-shape due to the solidification process. The TiB whiskers have a B27 crystal structure and grow along the B27 [010] direction. Based on Density Functional Theory (DFT), the surface energies of B27 (100), (101), (101¯) and (001) planes were calculated. The results show that the cross sections of TiB whiskers are hexagonal and consist of (100), (101), (101¯) planes.