Phase and structural transformations in a nanocrystalline alloy Fe72.5Cu1Nb2Mo1.5Si14B9

Abstract

The material for investigation was a ribbon with an amorphous structure obtained by the melt spinning technique from a melt of molybdenum-modified Finemet-type high-permeability Fe 72.5 Cu 1 Nb 2 Mo 1.5 Si 14 B 9 alloy. Using the methods of non-ambient X-ray diffraction, calorimetry, and dilatometry, temperature intervals of transformations during the transition of material from the amorphous state to the nanocrystalline one with subsequent recrystallization were determined. Each method was characterized by its own heating rate: 1 K / min for the non-ambient X-ray diffraction, 30 K / min for calorimetry, and 20 K / min for dilatometry. Regardless of the heating rate, phase and structure transformations (crystallization and recrystallization, respectively) were observed sequentially. With decreasing heating rate, the crystallization temperature significantly decreased and the recrystallization temperature slightly decreased. Specific heats of crystallization (386 kJ / mol) and recrystallization (88 kJ / mol) were calculated from calorimetry data. Basing on the results of X-ray diffraction and calorimetric studies, the possibility of using the structural unit model was analyzed to describe the amorphous state. It was supposed that any condensed state of the material (amorphous, nanocrystalline and recrystallized) were distinguished by different sizes of coherent scattering regions (CSRs). The lower estimate of coherent scattering regions size was made from the X-ray diffraction halo width for the amorphous state and (110) diffraction line broadening for polycrystals. The Wigner-Seitz cell (truncated octahedron) containing one atom has been adopted as a structural unit. Specific heats of transformations were compared to the values of energies related to the transitions of atoms from CSR borders to lattice sites. Satisfactory applicability of the structural unit model for the description of the amorphous state was demonstrated.

Nanocrystalline Soft Magnetic Iron-Based Materials from Liquid State to Ready Product

“…The volume fraction of the crystalline phase is about 0.7 [15]. Figure 10 shows the diffraction patterns of the Fe 72.5 Cu 1 Nb 2 Mo 1.5 Si 14 B 9 alloy during heating with a step of 25 K [61]. At temperatures below 725 K, the diffraction patterns have the form of halos, which correspond to the amorphous state.…”

Mechanism of Solid-State Amorphization in the Fe-Si-Cu-Mg-O System

“…Subsequent studies were shown, that metallic amorphous materials in some cases have superior mechanical, magnetic and anti-corrosion properties against conventional alloys [2]. At present, metallic glasses are produced by thousands of tons commercially [3] and they are used for the production of automobiles, sporting goods, and other products [4] Until the current time, the theory which explains atomic amorphous structure formation and its influence on properties of metallic glass, is the object for studies [5][6]. Despite much compositions of metallic glasses are already known [7], interest in the development of new amorphous, nanocrystalline materials [8] or current materials optimization [9] continued to be huge.…”

Thermo-Physical Parameters Determination of Nano-Crystalline Fe_72.5Cu₁Nb₂Mo_1.5Si₁₄B₉ Alloy for Twisted Magnetic Cores Heat Treatment Optimization

“…Physical and chemical metals properties in amorphous state varied significantly from its properties in amorphous state. At present, detailed theory which explains properties and phenomena in metal glasses is not developed and it is scientific research [6][7][8]. Interest to development new [9][10][11] and composition optimization of old amorphous metallic alloys [12][13][14], despite there are enough numerous currently known chemical compositions of amorphous metallic alloys [15][16][17].…”