Atomic structure evolution related to the Invar effect in Fe-based bulk metallic glasses

Abstract

The Invar effect is universally observed in Fe-based bulk metallic glasses. However, there is limited understanding on how this effect manifests at the atomic scale. Here, we use in-situ synchrotron-based high-energy X-ray diffraction to study the structural transformations of (Fe71.2B24Y4.8)96Nb4 and (Fe73.2B22Y4.8)95Mo5 bulk metallic glasses around the Curie temperature to understand the Invar effect they exhibit. The first two diffraction peaks shift in accordance with the macroscopically measured thermal expansion, which reveals the Invar effect. Additionally, the nearest-neighbor Fe–Fe pair distance correlates well with the macroscopic thermal expansion. In-situ X-ray diffraction is thus able to elucidate the Invar effect in Fe-based metallic glasses at the atomic scale. Here, we find that the Invar effect is not just a macroscopic effect but has a clear atomistic equivalent in the average Fe–Fe pair distance and also shows itself in higher-order atomic shells composed of multiple atom species.

X-ray Diffraction Computed Nanotomography Applied to Solve the Structure of Hierarchically Phase-Separated Metallic Glass

“…, the nanoscope end station. The data that support the findings of this study are available from the corresponding author upon reasonable request and are also made publicly available by ESRF …”

Controlling the Glassy State toward Structural and Mechanical Enhancement: Additive Manufacturing of Bulk Metallic Glass Using Advanced Laser Beam Shaping Technology

“…[3] Casting as a promising process has been applied to produce a wide range of Fe-, Cu-, Ti-, and Zr-BMGs. [4][5][6][7][8][9][10][11] Nevertheless, the maximum diameter of the fabricated samples is limited within the range of millimeters [12,13] for the many technologically relevant alloy systems.…”

Influence of Chemical Composition and Structure on the Cooperative Fluctuation in Supercooled Glass-Forming Liquids

“…The vitrification process depends on the molecular or atomic rearrangements in the deeply supercooled melt, which are usually described by spatially and temporally fluctuating associations of particles. Depending on the selected material and characterization method, these associations are referred to as Medium Range Order (MRO) correlation regions, , dynamic heterogeneities, or spatial heterogeneities, but all of them describe spatio-temporal domains in which the molecular or atomic mobility is not homogeneous , and drastically changes during the vitrification process. , These dynamic domains, the so-called Cooperatively Rearranging Regions (CRR), affect not only the kinetics of the glass transition (e.g., the fragility index) but also other properties, such as thermal expansion, microhardness, and any eventual subsequent crystalline structure . In other words, the stability and macroscopic properties of any amorphous system depend on their spatio-temporal nanostructure, i.e., on their nanoscale cooperative fluctuation.…”