Properties Of Bulk Amorphous Alloys Research Articles

The Magnetisation Process of Bulk Amorphous Alloys: Fe36+xCo36-xY8B20, Where: x = 0, 3, 7, or 12.

Amorphous Fe- and Co-based alloys possess so-called soft magnetic properties. Due to the high sensitivity of the magnetisation vector to any inhomogeneities occurring in these alloys, it is possible to assess indirectly structural defects. This paper presents the results of research on the structure and magnetic properties of bulk amorphous alloys with a high content of Fe and Co. The magnetic properties of the produced alloys were tested using a Faraday magnetic balance and a vibrating sample magnetometer (VSM). Analysis of the magnetisation process in the region known as the approach to ferromagnetic saturation was carried out in accordance with Kronmüller’s theorem. Magnetisation in magnetic fields of greater than the effective anisotropy field (Holstein-Primakoff para-process) was also studied. For the studied alloys, it was found that an increase in Fe content causesan increase in saturation magnetisation, and decreases in the values of the coercive field and thespin-wave stiffness parameter, Dspf. A relationship was observed between the width of the amorphous halo and the value of the coercive field. However, no significant links were found between either the presence of structural defects and the properties of these materials, or between the Co content and the value of the coercive field.

Relationship between the shape of X-ray diffraction patterns and magnetic properties of bulk amorphous alloys Fe65Nb5Y5+xHf5-xB20 (where: x = 0, 1,2, 3, 4, 5)

The evolution of the structure in ferromagnetic amorphous alloys is difficult to characterize and work is ongoing to describe it. Generally, in the literature on the subject it is difficult to find publications on the description of changes in the amorphous structure and their impact on magnetic properties. The paper presents results of research on the structure and magnetic properties of iron-based bulk amorphous alloys. Alloys with chemical composition Fe65Nb5Y5+xHf5-xB20 (where: x = 0, 1, 2, 3, 4, 5) were produced using the injection casting method. Structure of the materials was examined using X-ray diffraction. Magnetic properties were determined using a vibrating sample magnetometer. An attempt was made to relate the X-ray diffraction images with the magnetic properties of produced alloys. It has been shown that in the case of investigated alloys there is a relationship between the value of the coercive field and the width and location of the maximum corresponding to the amorphous phase. A similar relationship was found for the Curie temperature value. In addition, saturation magnetisation was found to be associated with maximum intensity.

EFFECT OF COPPER ADDITIVES ON IRREVERSIBLE MELTING IN [{(Fe0.5Co0.5)0.75B0.2Si0.05}96Nb4]100-xCux, x ≤ 3, ALLOYS

Iron and cobalt based ferromagnetic bulk amorphous alloys have received considerable interest nowadays in view of their useful properties for wide spread applications in magnet technology, shape memory alloys, high frequency communications at low power loss, and other devices. In this purview, here we report synthesis and thermal properties of bulk amorphous alloys [{( Fe 0.5 Co 0.5)0.75 B 0.2 Si 0.05}96 Nb 4]100-x Cu x (x = 0, 1, 2, and 3). A copper mould casting of molten alloy was used to obtain a vitrified alloy in form of thin rods (1–2 mm diameter). Amorphous structure retains at a cooling rate as low as 100 K/s in argon atmosphere. Heat out-put measured in terms of a differential scanning calorimetric signal during heating and cooling cycles of these alloys demonstrate irreversibility in a compositional dependent melting point, which follows the glass transition temperature and successive crystallization. The irreversibility persists in this specific example of the bulk amorphous alloys even on sufficiently slow heating or cooling rates such as 0.33 K/s in argon. The copper inclusion tailors the melting point, the enthalpy of the fusion, and other thermodynamic parameters. Results are analyzed in corroboration to the magnetic properties.

Improvement of the plasticity of bulk amorphous alloys via a low-angle shear-deforming process

This study examined the fundamental issue of whether an elastic shear stress imposed on an amorphous alloy causes structural changes during the process of quasistatic loading. A shear-deforming device that can deliver elastic shear stress to the workpieces was designed to investigate the effect of excess free volume generated by elastic shear stress on the mechanical properties of bulk amorphous alloys. With repeated application of elastic shear stress, the plasticity of the shear-deformed amorphous alloys increased, while the yield strength decreased. These behaviors were analyzed from the perspective of the structural changes associated with the viscoelastic nature of amorphous alloys.