A Review of Ultrafine-Grained Magnetic Materials Prepared by Using High-Pressure Torsion Method

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 mechanical properties. The HPT processing of magnetic materials and its influence on the structural and magnetic properties have attracted increasing research interest recently. This review describes the application of HPT to magnetic materials and our recent experimental results on Mn3O4, Mn4N, and MnAl-based alloys. After HPT, most magnetic materials exhibit significantly reduced grain size and substantially enhanced coercivity.

Structure and magnetic properties of nanocrystalline SmCo5 and SmCo3Cu2 prepared by using high-pressure torsion method

“…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.…”

Magnetic Materials via High-Pressure Torsion of Powders

“…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)…”

Some Unresolved Problems of High-Pressure Torsion

“…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.…”