Abstract:High-pressure torsion (HPT) is a severe plastic deformation technique where a sample is subjected to torsional shear straining under a high hydrostatic pressure. The HPT method is usually employed to create ultrafine-grained nano-structures, making it widely used in processing many kinds of materials such as metals, glasses, biological materials, and organic compounds. Most of the published HPT results have been focused on the microstructural development of non-magnetic materials and their influence on the mec… Show more
“…The high-pressure torsion method, first introduced by Bridgman in 1935, 18 has received extensive attention as a top-down severe plastic deformation (SPD) technique in creating ultrafine-grained micro-structures with novel physical properties. 19 HPT produces high-density crystal defects and grain boundaries, which acting as pinning points in preventing dislocation motion and/or magnetization reversal, leading to the improved strength and/or magnetic coercivity of materials. Recently, SmCo5-Cu/Fe magnets were produced by mixing SmCo5 and Cu or Fe powders followed by severe plastic deformation.…”
Nanocrystalline SmCo5 and SmCo3Cu2 alloys were prepared by using high pressure torsion (HPT) method. The effect of severe plastic deformation of HPT on the structure and magnetic properties of the samples were investigated systematically. The grain size of SmCo5 and SmCo3Cu2 alloys was refined to the nanocrystalline regime or even amorphous state by HPT, depending on the number of the HPT rotation. Lamellar microstructures of the grains were observed in the samples after HPT for 2 turns of rotation. With increasing number of HPT rotation, a further structural refinement and an increasing coercivity were observed. The coercivity of the as-cast SmCo5 and SmCo3Cu2 alloys after HPT reached up to 0.5 and 1.64 T, respectively. This work demonstrates that HPT is a high efficiency method in producing bulk nanocrystalline magnetic materials.
“…The high-pressure torsion method, first introduced by Bridgman in 1935, 18 has received extensive attention as a top-down severe plastic deformation (SPD) technique in creating ultrafine-grained micro-structures with novel physical properties. 19 HPT produces high-density crystal defects and grain boundaries, which acting as pinning points in preventing dislocation motion and/or magnetization reversal, leading to the improved strength and/or magnetic coercivity of materials. Recently, SmCo5-Cu/Fe magnets were produced by mixing SmCo5 and Cu or Fe powders followed by severe plastic deformation.…”
Nanocrystalline SmCo5 and SmCo3Cu2 alloys were prepared by using high pressure torsion (HPT) method. The effect of severe plastic deformation of HPT on the structure and magnetic properties of the samples were investigated systematically. The grain size of SmCo5 and SmCo3Cu2 alloys was refined to the nanocrystalline regime or even amorphous state by HPT, depending on the number of the HPT rotation. Lamellar microstructures of the grains were observed in the samples after HPT for 2 turns of rotation. With increasing number of HPT rotation, a further structural refinement and an increasing coercivity were observed. The coercivity of the as-cast SmCo5 and SmCo3Cu2 alloys after HPT reached up to 0.5 and 1.64 T, respectively. This work demonstrates that HPT is a high efficiency method in producing bulk nanocrystalline magnetic materials.
“…For further information and a more detailed discussion on dynamic interplay between microstructure evolution and magnetic properties, the interested reader is referred to some excellent review articles. [11,13,14,[17][18][19][20][21] 1. Magnetic mechanisms and microstructural tuning (microstructural tuning for magnetic hardening)…”
Magnets are key materials for the electrification of mobility and also for the generation and transformation of electric energy. Research and development in recent decades lead to high performance magnets, which require a finely tuned microstructure to serve applications with ever increasing requirements. Besides optimizing already known materials and the search on novel material combinations, an increasing interest in unconventional processing techniques and the utilization of magnetic concepts is apparent. Severe plastic deformation (SPD), in particular by high-pressure torsion (HPT) is a versatile and suitable method to manufacture microstructures not attained so far, but entitling different magnetic coupling mechanisms fostering magnetic properties. In this work, we review recent achievements obtained by HPT on soft and hard magnetic materials, focusing on powder as starting materials. Furthermore, we give specific attention to the formation of magnetic composites and highlight the opportunities of powder starting materials for HPT to exploit magnetic interaction mechanism.
“…4) The results of recent studies on the applications of HPT for producing advanced materials of different categories were surveyed in a number of publications. They refer to thermoelectric generators, 5) magnetic materials, 6) high entropy alloys, 7) hydrogen storage materials, 8,9) superconducting materials, 10) semiconductors, 11) and hybrid nanocrystalline alloys. 12) Besides, review articles focusing on various aspects of HPT were published.…”
This overview highlights some salient features of one of the most popular severe plastic deformation techniques: high-pressure torsion (HPT). It focuses on the unresolved challenging problems of HPT. The problems selected touch upon some fundamental questions of mechanics of plasticity, fracture, and friction that are at the core of the HPT process. The scientific significance of these problems and the proposed pathways to resolving them are discussed. The article is meant to promote the use of HPT as a potent tool for studying plasticity at large strains theoretically and also as a practical method enabling novel micromanufacturing routes.
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