Development of nanocrystalline Al-Ti alloy powders by reactive ball milling

Elemental powders of Al and Ti were mechanically alloyed in a hydrogen atmosphere to produce nanocrystalline Al-Ti alloys. A brittle hydride phase(TiH)(2) was formed and well dispersed by a solid-gas reaction during initial milling. The particle size was effectively reduced by the formation of TiH(2) and the grain size in the particles became nanoscale with progression of the milling. High resolution transmission electron spectroscopy (HREM) analysis showed the presence of TiH(2) at the boundaries of Al or Al(3) Ti grains. This phase is considered to not only reduce the particle size but also to impede the grain growth during the heat treatment. Decomposition of TiH(2) and subsequent formation of Al(3)Ti occurred at 440-480 degrees C. However, the heat treated powders maintained their nano-sized structure. (C) 1998 Elsevier Science S.A.