In situ structural investigation of amorphous and nanocrystalline Fe40Co38Mo4B18 microwires

Abstract

Thermal evolution of the structure of glass-coated nanocrystalline FeCoMoB microwire during its devitrification has been studied. It is shown that annealing at the temperature above 411 o C leads to the formation of crystalline α-FeCo grains with diameter ~ 12 nm. Annealing at higher temperature increases the crystalline weight fraction up to 40% at 565 o C. However, crystalline grains size increases very weakly to ~ 13 nm. The thermal expansion coefficient of nanocrystalline microwire decreases by one half comparing to that of the amorphous precursor.

In situ XRD studies of nanocrystallization of Fe-based metallic glass: a comparative study by reciprocal and direct space methods

“…Another three parameters were used to account for a quadratic polynomial describing background and one scaling parameter was used to adjust the contribution from the amorphous matrix. A similar approach was previously used by Michalik et al 27 when studying the crystallization behavior of glassy microwires using in-situ XRD. As can be seen from Fig.3a, the proposed model satisfactorily describes the XRD profile.…”

Temperature-Induced Short-Range Order Changes in Co67B33 Glassy Thin Films and Elastic Limit Implications

“…[4] Mechanical properties of metallic glasses at elevated temperatures have been investigated by a small sample compression test [4,6] or extrusion. [7] Furthermore, the temperature-dependent short-range order has been studied by high-energy X-ray diffraction (XRD) [8,9] or molecular dynamic *Corresponding author. Email: schnabel@mch.rwth-aachen.de (MD) simulation.…”

“…The objective of this work is to identify the temperature-induced topological evolution of the Co 67 B 33 metallic glass thin films, to enable knowledgebased design of new metallic glasses with high strength and plasticity at room temperature. To this end, we employ in situ high-temperature, high-energy XRD experiments [9] in combination with ab initio MDs simulations. [14] Experimental Methods Co 67 B 33 metallic glass thin films were synthesized by magnetron sputtering, using a ultra-high vacuum system with a base pressure of 4 · 10 −5 Pa. Elemental targets, with a diameter of 2 in.…”

Effect of Current Annealing on Domain Structure in Amorphous and Nanocrystalline FeCoMoB Microwires

“…Small variations of resistance at current density below 400 MA/m 2 reflect the structural relaxation (stress relief and homogenization) of the amorphous structure. Above 400 MA/m 2 , the resistance steeply decreased as a result of crystallization of bcc-(Fe,Co) crystalline grains [10]. It is worth to note that crystallization current density ≈ 400 MA/m 2 corresponds to the crystallization temperature ≈ 420…”

“…Such annealing leads to the appearance of bcc-(Fe,Co) grains with very small diameter 12-13 nm embedded in the residual amorphous matrix [10]. Created grains are too small and well separated to interact between them through exchange interaction.…”