Development of Amorphous and TiAl-Nb<sub>2</sub>Al Intermetallic Nanocomposite Powders by Mechanical Alloying

Abstract

Present investigation was focused on to synthesize TiAl-Nb2Al nanocomposite powders by high energy ball milling from a mixture of prealloyed TiAl, niobium, aluminium and SiC powders. Systems chosen with different Nb and Al concentrations were processed at optimized ball milling parameters. The synthesized powders were characterized with the help of X-ray diffraction (XRD), electron microscopy, differential thermal analysis (DTA) to understand the milling behaviour of TiAl / TiAl-Nb-Al-SiC systems. High energy ball milling of prealloyed TiAl powder resulted nanocrystalline structure at early time intervals (10hrs) and sustained up to 50hrs. TiAl-Nb-Al-SiC systems exhibited amorphous structure in lower Nb content and formation of Nb2Al nanocrystalline compound with increasing Nb and Al additions. Stability of TiAl covalent bonded intermetallic compound was weakened by dissolution of Nb in the matrix and resulted amorphous structure. The final product contained nanocrystalline TiAl, amorphous structure and TiAl-Nb2Al intermetallic nanocomposite powders with varying Nb and Al concentrations.