Impact of severe plastic deformation on microstructure and hydrogen storage of titanium-iron-manganese intermetallics

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

“…As mentioned earlier, the HPT-synthesized TiFe is activated by only one cycle evacuation at 673 K for 2 h, whereas the as-cast pure TiFe is usually activated by repeated exposure to vacuum and hydrogen atmosphere at high temperatures. [4][5][6][7][8][9][10] However, HPT-processed TiFe ingot can absorb hydrogen without any need to thermal activation, [23][24][25] suggesting that the application of HPT to TiFe ingot as a processing tool is more effective than the application of HPT as a mechanical alloying tool for easy activation. Here, it should be noted that both applications of HPT to activate TiFe ingot and to synthesize TiFe were conducted under air atmosphere, and X-ray photoelectron spectroscopy already confirmed that a oxide layer is formed even when the bulk ingot is processed by HPT.…”

“…[4][5][6] In 1974, the first successful results on hydrogen storage in TiFe at room temperature were reported by Reilly and Wiswall, but they found that the as-cast material should be activated by repeated exposure to vacuum and hydrogen atmosphere at temperatures as high as 673 K. [4] Later studies also showed that despite all advantages of TiFe, its difficult activation is a main drawback. [7][8][9][10] There have been several attempts to solve the activation problem of as-cast TiFe mainly using two strategies: 1) chemical activation by addition of a third element, such as Pd, [11] Ni, [12] Mn, [13][14][15][16] and Zr [17][18][19] and 2) mechanical activation by ball milling, [20][21][22] high-pressure torsion (HPT), [23][24][25] and cold rolling. [26,27] Although the exact mechanism for the activation of TiFe is still under argument, it is generally believed that the first strategy is based on the surface catalytic performance of elemental additives, and the second strategy is based on nanostructuring and introduction of hydrogen pathways into bulk, such as cracks, nanograin boundaries, and amorphous regions.…”

“…[26,27] Although the exact mechanism for the activation of TiFe is still under argument, it is generally believed that the first strategy is based on the surface catalytic performance of elemental additives, and the second strategy is based on nanostructuring and introduction of hydrogen pathways into bulk, such as cracks, nanograin boundaries, and amorphous regions. Motivated by earlier studies on the application of the HPT method to as-cast TiFe, [23][24][25] in this study and for the first time, we synthesize the TiFe hydrogen storage materials from the Ti and Fe powders by the HPT method and examine its activation (see the principles of HPT in the previous studies [28,29] ). It should be noted that HPT as a severe plastic deformation (SPD) method shows high potential to produce nanostructures, [30,31] control phase transformations, [32,33] and achieve solid-state reactions.…”

Finte element modeling of the behavior of polymethyl-methacrylate (PMMA) during high pressure torsion process.

“…The occurrence of superplasticity was reported not only after HPT processing of thin disc specimens [7,8], but also using the ring samples [9,10], bulk samples [11,12] as well as after continuous high-pressure torsion extrusion [13]. Different materials have been tested experimentally [14] and theoretically [15] through the application of HPT process such as aluminum alloys [8,16], nickel [17], copper [15], titanium alloys [3,18], polymers [19], zirconium [20,21], Magnesium alloys [22], aluminum-zinc alloys [23], intermetallics [24,25] and others (see [26,27]). In the past, FEM simulations of the SPD processes were performed with the purpose of analysis and optimization of the SPD processing variables and prediction of the mechanical and microstructural characteristics of the SPD processed samples [15].…”

Mechanical Synthesis and Hydrogen Storage Characterization of MgVCr and MgVTiCrFe High‐Entropy Alloy

“…To get better activation, the HPT process was applied on the samples after HEBM. Earlier studies showed that the HPT method is not only effective to synthesize hydrogen storage materials but also to enhance the activation procedure . More details about the background of HPT can be found in the previous studies .…”