Nanocrystalline and amorphous structure formation in Ti–Al system during high energy ball milling

The aim of the present work was to study the structural evolution of Ti–48Al (at.-%) powder blend during mechanical alloying. Because milling parameters play a vital role in achieving the desired structure/phase, milling was carried out with optimised parameters. Both powder handling and milling operations were performed under high pure argon atmosphere to prevent oxidation of the powder blend. Mechanically alloyed powder blend was then characterised by scanning electron microscope (SEM), X-ray diffraction (XRD) and differential thermal analyzer (DTA). Mechanical alloying induced severe plastic deformation resulting in cold welding, powder particle refinement and narrowing of powder particle size distribution as is evidenced from SEM micrographs. XRD analysis indicated complete dissolution of aluminium in titanium at 20 h of milling and achieving nanostructure before amorphous phase formation. DTA scan indicated the disappearance of one of the exothermic peaks, and a gradual drop in crystallisation temperature with increasing milling time.