LATTICE DESTABILIZATION AND AMORPHIZATION BY MECHANICAL ALLOYING IN THE TI-AL SYSTEM

Analytical electron microscopy and X-ray diffraction techniques have b een used to study the amorphization process of the Ti-Al system induce d by mechanical alloying. The results show that the entire transformat ion develops from the diffusion of Al into the Ti crystal lattice, beg inning as soon as a well-developed layered structure is formed in the powders in the early milling stages (after 6 h). Collapse of the highl y distorted host lattice occurs after milling for 20 h and gives rise to a homogeneous amorphous structure at 24 h. Further milling time (34 h) produces an f.c.c. nanocrystalline phase with a Ti-Al at. ratio of approximately 3 and with the lattice parameter a=0.42 nm.