The effect of rolling strain on the development of Ti-Al-Nb ultrafine grained intermetallic composites

Ultrafine grained Ti-Al-Nb intermetallic composites were processed by cold roll bonding and reaction annealing of elemental Ti, Al and Nb foils to produce Ti-46AI-9Nb (at%) alloys. The microstructure and phase development during cold rolling and reaction annealing were characterized by scanning electron microscopy equipped with energy dispersive spectroscopy (SEM/EDS), transmission electron microscopy (TEM), and x-ray diffraction (XRD). With increasing reduction in thickness, more Ti Al-3 phase was produced at the Ti/Al interfaces. But at the Ti/Nb and Nb/Al interfaces, there is no such difference among the reaction layers. It is suggested that rolling strain has a significant effect on the formation of Ti Al-3, but little effect on the formation of NbAl3. The TEM study revealed that after 80% reduction, the grain size is less than I gm and the whole areas were filled with ultrafine grained crystals.