Synthesis of Nanostructured TiFe Hydrogen Storage Material by Mechanical Alloying via High-Pressure Torsion

TiFe as a room-temperature hydrogen storage material is usually synthesized by ingot casting in the coarse-grained form, but the ingot needs a thermal activation treatment for hydrogen absorption. Herein, nanograined TiFe is synthesized from the titanium and iron powders by severe plastic deformation (SPD) via the high-pressure torsion (HPT). The phase transformation to the TiFe intermetallic is confirmed by X-ray diffraction, hardness measurement, scanning/transmission electron microscopy, and automatic crystal orientation and phase mappings (ASTAR device). It is shown that the HPT-synthesized TiFe can store hydrogen at room temperature with a reasonable kinetics, but it still needs an activation treatment. A comparison between the current results and those achieved on high activity of HPT-processed TiFe ingot suggests that a combination of ingot casting and SPD processing is more effective than synthesis by SPD to overcome the activation problem of TiFe.