Metastable phase-assisted nucleation in a near-alpha titanium matrix composite with network architecture

The secondary alpha (α _s ) phase is an important component of a novel TiBw/TA15 composite with network architecture. In order to investigate the precipitation mechanism of the α _s phase, the microstructure after multi-directional forging was characterised by EPMA, EBSD, and TEM. The results showed that several differently sized α _s phases separated out from the (Mo and V)-enriched phase, which was composed of a nano-sized metastable omega phase along with some retained beta phase. It could be also found that the metastable omega phase would transform to the alpha phase when adequate activation energy was provided. The precipitation mechanism of the α _s phase in this composite has been discussed in detail and it can be inferred as an omega-assisted heterogeneous nucleation process. This paper is part of a thematic issue on Titanium.