Stability of strengthening effect of in situ formed TiCp and TiBw on the elevated temperature strength of (TiCp + TiBw)/Ti composites

• The phase constitution of Ti–B4C composite was clarified by different methods.
• Pining effect of TiCp and TiBw is effective to prevent Ti matrix from coarsening.
• The strengthening effect of TiCp and TiBw is stable at elevated temperatures.

(TiCp + TiBw)/Ti composite was firstly prepared by spark plasma sintering (SPS) and hot extrusion from Ti–B4C system, and then isothermally heat treated at 400–700 °C for 24 h, respectively. The elevated temperature tensile strength was tested at temperatures corresponding to isothermal heat treatments. Microstructure characterizations were carried out by using SEM, EPMA, XRD, EBSD and TEM. Results show that, the microstructure of (TiCp + TiBw)/Ti composite consists of Ti matrix, particle-like TiC and whisker-like TiB. TiCp and TiBw are stable at elevated temperatures and can prevent Ti matrix from coarsening. On the other hand, the strength of the composite decreases significantly with the increase of testing temperature, but it is always in proportion to that of pure Ti tested at the same temperature, indicating the strengthening effect of in situ formed TiCp and TiBw is stable at elevated temperature. The decrease of elevated temperature strength of (TiCp + TiBw)/Ti composite can be mainly attributed to the high temperature softening of Ti matrix.