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.
Highlights
IntroductionMetallic glasses (MGs) are a well-established type of material, characterized by their lack of long-range order structure, that can be produced in several physical forms (powders [1], ribbons [2], coatings [3], microwires [4,5], bulks [6], magnetorheological fluids [7], etc.) and have a potential variety of applications in several fields: (a) magnetism, including sensors or choke coils [8,9]; (b) electrocatalysis, for example, in fuel cells [10]; (c) biomedicine with stents or orthopedic surgeries [11,12,13,14], (d) engineering, for example with the development of micro electro-mechanical (MEMs) devices [15] and in environmental applications like the catalytic degradation of toxic organic molecules [16] or radiation shielding properties of newly developed FeBCSiP alloys [17]
FeCoSiB(Nb,Zr,Mo) metallic glasses have been produced in ribbon shape in order to study their amorphous structure and their crystallization by means of Transmission Mössbauer Spectroscopy (TMS) and shed some light on the effects of the different elements (Nb, Zr and Mo) on this Fe-based metallic glass
The crystallization behavior is, as expected, the same as the one observed in the same compositions produced as bulk metallic glasses [33]
Summary
Metallic glasses (MGs) are a well-established type of material, characterized by their lack of long-range order structure, that can be produced in several physical forms (powders [1], ribbons [2], coatings [3], microwires [4,5], bulks [6], magnetorheological fluids [7], etc.) and have a potential variety of applications in several fields: (a) magnetism, including sensors or choke coils [8,9]; (b) electrocatalysis, for example, in fuel cells [10]; (c) biomedicine with stents or orthopedic surgeries [11,12,13,14], (d) engineering, for example with the development of micro electro-mechanical (MEMs) devices [15] and in environmental applications like the catalytic degradation of toxic organic molecules [16] or radiation shielding properties of newly developed FeBCSiP alloys [17]. The Mössbauer signal is directly proportional to the number of Fe atoms present in each phase, allowing the quantification of the relative amount of Fe atoms in a particular region, either crystalline or amorphous This technique has been successfully used in combination with other conventional characterization techniques like x-ray diffraction or differential scanning calorimetry to offer a comprehensive view of the structure and phase formation in metallic glasses [26,29,38,39,40] and in many Fe-containing alloys [41,42,43]. FeCoSiB(Nb,Zr,Mo) metallic glasses have been produced in ribbon shape in order to study their amorphous structure and their crystallization by means of Transmission Mössbauer Spectroscopy (TMS) and shed some light on the effects of the different elements (Nb, Zr and Mo) on this Fe-based metallic glass
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