COMPACTION AND CHARACTERIZATION OF MECHANICALLY - ALLOYED NANOCRYSTALLINE TITANIUM ALUMINIDES

Blended elemental (BE) Ti-24 at; pet Al-ii at. pet Nb (Ti-24-11) and T i-55 at. pet-Al (Ti-55) powders and prealloyed (PA) Ti-24-11 powders w ere mechanically alloyed in a SPEX mill or an attritor. After SPEX mil ling for 10 hours, the BE Ti-24-11 powder contained the B2/bcc phase, while the BE Ti-55 powder showed the presence of an amorphous phase. T he PA Ti-24-11 powder containing the B2 phase showed a decrease of cry stal size on milling. These powders were consolidated by hot isostatic pressing (''hipping''), Ceracon process, and dynamic methods. On comp action,,the B2/bcc phase in the Ti-24-11 sample transformed to a mixtu re of the B2 and orthorhombic (''O''), phases, while the amorphous pha se in the Ti-55 powder crystallized to a mixture of the gamma-TiAl and alpha(2)-Ti3Al phases. The finest grain size in compacted material wa s obtained in the dynamically consolidated powder, and the grain size in the-hot isostatic pressed (''hipped'') powder became larger with th e increasing hipping temperature.