Time-Resolved X-Ray Diffraction Studies on the Crystallization of Amorphous FeSiB-Based Alloys

Abstract

The influence of separate and combined addition of Cu and Nb on the crystallization behaviour and the kinetics of Fe3Si formation in the system Fe77.5‐x‐ySi15.5B7CuxNby is investigated by means of X‐ray diffraction. Addition of Cu decreases the thermal stability of the amorphous matrix, the microstructure after crystallization is unchanged. Nb controls the microstructure. The onset of the two crystallization stages and the chemistry of the product of the second crystallization stage are dependent upon the concentration of Nb. Combined addition of Cu and Nb is responsible for coexistence of nanocrystalline Fe3Si precipitations and the amorphous matrix over a wide temperature range. The formation of Fe3Si is described in terms of Johnson‐Mehl‐Avrami kinetics (JMA). The Avrami exponent n is affected by addition of Cu, between 410 and 430 °C it is reduced from 1.4 to 0.7. On addition of Nb n is found to be ≈ 1. The combined addition of Cu and Nb results in an Avrami exponent n = 0.7 independent of annealing temperature (T = 475 to 600 °C).

Small-Angle X-ray Scattering Study of Nanocrystalline and Amorphous States of the Fe73.5CuNb3Si13.5B9 Alloy

“…Crystallization processes in the Fe-Cu-Nb-Si-B alloy have been studied using several techniques, such as differential thermal analysis, M6ssbauer spectroscopy, X-ray diffraction and X-ray absorption spectroscopy (Herzer, 1990;Noh, Pi, Kim & Kang, 1991;Miiller, Mattern & Illgen, 1991;Hampel, Pundt & Hesse, 1992;Knobel, dos Santos, Torriani & Turtelli, 1993;Ayers, Harris, Sprague & Elam, 1994;Danzig & Mattern, 1995). In the work described herein, we used small-angle X-ray scattering (SAXS) to perform structural investigations on this metallic alloy in different initial amorphous states and also during the annealing, which yields the state of the material that presents the best soit magnetic properties.…”

A Review of Different Models Derived from Classical Kolmogorov, Johnson and Mehl, and Avrami (KJMA) Theory to Recover Physical Meaning in Solid‐State Transformations

“…Although first postulate of Kolmogorov assumes a complete transformation of the system, this restriction is generally overseen after normalizing the transformed fraction to 1 at the end of the considered process by dividing the actual transformed fraction by the final one, . In fact, KJMA analysis was widely applied to primary crystallization, [ 44–51 ] precipitation, [ 52–58 ] eutectoid, [ 59,60 ] and quasicrystals formation [ 61 ] using this normalization. This yields an extra source of error in the data, as the final transformed fraction must be measured.…”

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

“…With time, silicon diffuses into the crystalline phase and the silicon content in the solid solution increases to 20 at. % [59,60]. At the final stage of nanocrystallization, grains are formed, the composition of which is close to Fe 80 Si 20 and Fe 3 Si, surrounded by a residual amorphous matrix.…”