Growth of semicoherent TiFe nanoparticles in β-Ti matrix

Thin Ti₇₃Fe₂₇ ribbons were prepared by rapid quenching from the melt. The as-quenched ribbons were in metastable condition with a small amount of nanoparticles of TiFe embedded in the β -Ti matrix. The β-Ti phase was oversaturated with Fe, and the amount of this phase was higher than the equilibrium value. High resolution imaging of the interface between TiFe and β-Ti showed that a periodic array of dislocations were present in the boundary to accommodate the lattice mismatch. The spacing between the dislocations in as-quenched specimen was 4.8 nm. When the ribbon was heated to 700°C, growth of the TiFe nanoparticles in 13-Ti matrix took place. The amount of β-Ti was reduced, as well as the Fe content in β-Ti. The interface between TiFe and β-Ti remained semicoherent, except that the spacing between the edge dislocations was reduced to 3.4 nm. The persistence of the semicoherent interface was ascribed to the same crystal structure and close lattice parameters of TiFe and β-Ti. Prolonged heating of the ribbon below the eutectoid temperature led to transformation of β-Ti to α-Ti.