Bulk-State Reactions and Improving the Mechanical Properties of Metals through High-Pressure Torsion

Abstract

This report presents an overview of recent studies demonstrating a bulk-state reaction involving mechanical bonding through the application of high-pressure torsion (HPT) processing on two dissimilar engineering metals. This processing approach was developed by revising the sample setup and applying the simple procedure of alternately stacking two different metal disks using several different metal combinations. Thus, this report describes the development in microstructure after the bulk-state reactions and the mechanical properties of the HPT-induced AlMg, AlCu, AlFe and AlTi alloy systems. A microstructural evaluation confirmed the capability of the HPT procedure for the formation of heterostructures across the disk diameters in these processed alloy systems. Tribology tests and hardness values together with density measurements demonstrated an improved wear resistance and an exceptional specific strength in these alloy systems. The bulk-state reaction by HPT demonstrates a considerable potential for the bonding of dissimilar metals and the fabrication of unique metal systems.

High‐pressure torsion of SiO2 quartz sand: Phase transformation, optical properties, and significance in geology

“…However, the grain size is drastically reduced after HPT processing and the number of diffracted points in the SAED analysis are increased to form a ring pattern in Figure 4D (this pattern was taken from the d area in Figure 4B). Grain refinement by HPT processing is a result of plastic strain effect, which was reported in various metallic 53–55 and nonmetallic 56–58 materials. On the contrary, in Figure 4E, the diffraction points in SAED disappear and a hollow pattern corresponding to amorphous SiO 2 appears (this pattern was taken from the e area of Figure 4B).…”

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

“…The elemental mixing improves with increasing the distance from disc center, indicating the importance of shear strain on mechanical alloying and controlling the phase transformation, in good agreement with earlier publications. [32][33][34][35] The microstructure of sample processed by HPT for ten turns was examined in detail using transmission electron microscopy (TEM), as shown in Figure 4, in different modes, such as bright-field imaging (Figure 4a), selected area electron diffraction (SAED) analysis (Figure 4b), dark-field imaging (Figure 4c), automatic orientation mapping (Figure 4d), and phase mapping ( Figure 4e) using an automatic crystal orientation and phase mappings (ASTAR device). Note that the phase map was overlaid with the reliability map in Figure 4e, and thus, the black regions in the image correspond to the phases that could not be identified with high reliability.…”

“…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. [34,35] The method was used successfully by the group of authors to synthesize various kinds of nanostructured intermetallics in different systems, such as Al-Ni, [36] Al-Ti, [37] Al-Cu, [38] Al-Ti-Ni, [39] Fe-Ni, [40] Mg-Ti, [41,42] Mg-Zr, [43] Mg-Hf, [44] Mg-Ni-Pd, [45] and Mg-V-Cr.…”

Synthesis of Hybrid Nanocrystalline Alloys by Mechanical Bonding through High‐Pressure Torsion

“…Table 1. The measured density, the maximum Vickers hardness value, and the estimated strength-to-weight ratio for the Al-Mg system [38] after HPT for 5-20 turns, Al-Cu system [40] after 20 and 60 HPT turns, and Al-Fe system [62] after HPT for 20 turns with the reference materials of Al-1050 and ZK60 alloys after HPT for 5 turns and CP Cu and CP Fe after HPT for 10 turns. Al/Mg/Al (HPT: 5 turns) [38] 2.50 130 170…”

“…Several earlier studies measured the densities of the mechanically bonded alloys of the Al–Mg, Al–Cu, and Al–Fe systems and the estimated strength‐to‐weight ratio for these alloy systems by applying their estimated yield strength using the measured Vickers microhardness values. A summary of these results is shown in Table where, for comparison purposes, the tabulation gives the density, Vickers microhardness, and specific strength for the base metals of Al, Mg, and Cu alloys after HPT for the high numbers of turns.…”