Precipitation behavior of silicide and synergetic strengthening mechanisms in TiB-reinforced high-temperature titanium matrix composites during multi-directional forging

Abstract

To investigate the precipitation behavior of silicide and evaluate the contribution of the reinforcement phase to the properties of titanium matrix composites, a TiB-reinforced high-temperature titanium matrix composite was prepared by vacuum induction melting and multi-directional forging. The microstructure of the resultant composite after multi-directional forging was composed of a spheroidized α-phase, uniformly-distributed TiB and dual-scale silicides. The precipitation of silicides was attributed to the acceleration of elemental diffusion due to dislocations during forging. The strength of the composite after multi-directional forging at room temperature increased by about 151.9 MPa due to the fine-grain strengthening of the α-phase and the precipitation strengthening of the silicides, whereas the load-bearing efficiency of the TiB whiskers was reduced with the decrease in the aspect ratio. The strength of the multi-directional-forged titanium matrix composite at 700 °C was reduced by about 28.3 MPa. However, its plasticity was significantly improved, and the elongation reached 116.8%. The main reasons for the decrease in the strength were the easy initiation of cracks the grain boundaries and the weakening of the precipitation strengthening of the silicides.