Structure evolutions in a Ti–6Al–4V matrix composite reinforced with TiB, characterised using high energy X-ray diffraction

A titanium matrix composite reinforced with TiB was produced using powder metallurgy. A Ti–6Al–4Valloy was chosen to be the matrix, and 12 wt.% of TiB$_{2}$ was used as the boron source for the solid stateformation of TiB. The TiB$_{2}$ to TiB conversion reaction was studied using an in situ high energy X-ray diffractiontechnique while heat treating the composite. The TiB$_{2}$ (space group: P6/mmm) converts into TiBB27(Pnma), via TiB-B$_{f}$ (Cmcm). The metastable character of B$_{f}$ is confirmed here; it is the first phaseformed during the conversion and it progressively converts into B27 during elevated temperature heattreatment. A modification of the phase transformation kinetics in the matrix and of the composite b transustemperature (T$_{\beta}$ = 1275 °C) was also observed, mainly due to gas contamination and intensive workhardening as a result of the mechanical alloying process used to manufacture the material and to a modificationof the matrix equilibria