Evaluation of the Effect of Minor Additions in the Crystallization Path of [(Fe0.5Co0.5)0.75B0.2Si0.05]100-xMx Metallic Glasses by Means of Mössbauer Spectroscopy

Abstract

Understanding the crystallization of metallic glasses is fundamental in the design of new alloys with enhanced properties and better glass-formability. The crystallization of a series of Fe-based metallic glasses of composition [(Fe0.5Co0.5)0.75B0.2Si0.05]100-xMx (M = Mo, Nb and Zr) has been studied by means of differential scanning calorimetry and transmission Mössbauer spectroscopy. This latter technique allows the following of the microstructural evolution of the studied alloys through the identification and quantification of the several Fe-containing crystalline phases and also through the changes in the amorphous structure at the initial stages of crystallization. The results show that the crystallization products are the same for all the studied compositions (α-Fe, Fe2B, (FeCo)23B6 and a paramagnetic remnant) although with different relative proportions and the crystallization of a phase without Fe in the alloys with Zr. Moreover, the addition of Zr favors the crystallization of α-Fe causing a detrimental effect on the glass forming ability, while the increase in Mo content up to 6 at% favors the crystallization of (FeCo)23B6. The different amount of α-Fe and borides is presented as a measure of the glass forming ability of this type of alloys.

Changes in the Surroundings of the Central Iron Atom in Amorphous Alloys

“…However, materials with an amorphous structure are characterized by the lack of boundary grains in their structure, unlike materials with a crystalline structure of the same chemical composition. Metallic glasses have been studied for many decades [1][2][3][4] in various respects, i.e., magnetic and mechanical properties, structural system, and thermal stability, using various types of measurement methods, including X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Mössbauer spectrometry, etc. [3][4][5][6][7].…”

“…Metallic glasses have been studied for many decades [1][2][3][4] in various respects, i.e., magnetic and mechanical properties, structural system, and thermal stability, using various types of measurement methods, including X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Mössbauer spectrometry, etc. [3][4][5][6][7]. It is also known that the properties of amorphous alloys can be improved by applying appropriate annealing at temperatures below the crystallization temperature.…”