PRODUCTION OF TI-48 MOL-PERCENT-AL INTERMETALLIC COMPOUND BY MECHANICAL MILLING AND VACUUM HOT-PRESSING OF TITANIUM HYDRIDE AND ALUMINUM POWDERS

A Ti-48 mol%Al intermetallic compound was produced by a mechanical mil ling (MM) process using titanium hydride and aluminum powders. Microst ructure change during heating of the Ti-48 mol%Al MM powder particles as well as microstructure of the MM powder particles and the vacuum ho t pressed compact were investigated. Almost 95% of the MM powder was y ielded by this process. Approximately 20% of the titanium hydride powd er dehydrogenated and changed to an alpha-Ti phase during the milling process, followed by the dispersion of an ultra-fine mixture of the ti tanium hydride and alpha-Ti particles within an aluminum powder partic les. Mean particle sizes of the titanium hydride and alpha-Ti particle s in the MM powder particles were approximately 6 nm in diameter. Diff erential scanning calorimeter analysis and X-ray diffraction analysis revealed that dehydrogenation took place between 600 K and 900 K, and a Al3Ti phase formed by the reaction of the a-Ti and aluminum phases. The vacuum hot press compact sintered at 1173 K showed a fine equiaxed (TiAl + Ti3Al) microduplex structure with a grain size of approximate ly 750 nm.