Electrochemical hydriding of nanocrystalline TiFe alloys

Nanocrystalline TiFe alloys with different morphology and microstructure were synthesized by mechanical alloying from the elemental powders with varied milling time. The particle morphology distinctly changes from globular to slaty between the 10th and 15th h of milling and then becomes spherical again after 30 h. The average particle size decreases continuously with milling time from about 50 μm (10 h milling) to 1–2 μm for the 30 h milled sample. X-ray diffraction analysis showed that after 15 h of milling alloying has already started. The initial mixture of metal powders transformed into amorphous or fine nanocrystalline material after 20 h. Further milling did not change the microstructure noticeably, i.e. it remaied nanocrystalline with some amount of amorphous fraction. Nanocrystalline Fe was also present in the end product. DTA analysis displayed exothermic effects due to crystallization reactions, revealing that the end product also contains the amorphous phase.