Microstructure and tensile properties of in situ synthesized (TiC + TiB + Nd2O3)/Ti-alloy composites at elevated temperature

A novel (TiC + TiB + Nd2O3)/Ti-alloy composites were in situ synthesized utilizing the reaction between Ti, C, Nd and B2O3 through homogeneously melting in a non-consumable vacuum arc remelting furnace. Ti–6.6Al–4.6Sn–4.6Zr–0.9Nb–1.0Mo–0.32Si alloy was chosen as the matrix Ti-alloy. The phases were identified by X-ray diffraction (XRD). The microstructures were examined by means of optical microscopy (OM), scanning electron microscopy (SEM) and backscattered electron microscopy. There are three kinds of reinforcements: TiC with near-equiaxed shape, TiB with whisker shape and Nd2O3 with sphere shape. Tensile properties of the as-cast composites were tested with strain rate 0.001 s−1 at 600, 650 and 700 °C. The results showed the tensile strength of the composites increased significantly at elevated temperature while keeping good plasticity. With the temperature increases, the improvement in tensile strength decreases. The fracture surfaces were examined by scanning electron microscopy. The fracture mechanism of composites turns from reinforcements’ crack to reinforcements’ debonding between 650 and 700 °C.