Phase development in titanium by mechanical alloying under hydrogen atmosphere

Titanium hydride was successfully synthesized at room temperature by ball milling. X-ray diffraction patterns demonstrated that a transformation of elemental Ti powders into TiH 2 could be induced at room temperature by ball milling under a hydrogen atmosphere. Almost no hydrogen absorption was observed during the initial few minutes of the milling process on the basis of x-ray diffraction patterns and hydrogen pressure in the reservoir system, although the grain size of Ti decreased significantly. A non-stoichiometric titanium hydride with an approximate composition of TiH 1.9 was first formed after about 7 min of milling and existed together with unhydrided Ti flakes. The stoichiometric hydride phase TiH 2 was developed after further milling at room temperature. Due to the trapping of hydrogen by numerous defects and grain boundaries, the dilute solution Ti(H) does not exist in the nanograin milled metal powders.