In situ correlation between metastable phase-transformation mechanism and kinetics in a metallic glass

Abstract

A combination of complementary high-energy X-ray diffraction, containerless solidification during electromagnetic levitation and transmission electron microscopy is used to map in situ the phase evolution in a prototype Cu-Zr-Al glass during flash-annealing imposed at a rate ranging from 102 to 103 K s−1 and during cooling from the liquid state. Such a combination of experimental techniques provides hitherto inaccessible insight into the phase-transformation mechanism and its kinetics with high temporal resolution over the entire temperature range of the existence of the supercooled liquid. On flash-annealing, most of the formed phases represent transient (metastable) states – they crystallographically conform to their equilibrium phases but the compositions, revealed by atom probe tomography, are different. It is only the B2 CuZr phase which is represented by its equilibrium composition, and its growth is facilitated by a kinetic mechanism of Al partitioning; Al-rich precipitates of less than 10 nm in a diameter are revealed. In this work, the kinetic and chemical conditions of the high propensity of the glass for the B2 phase formation are formulated, and the multi-technique approach can be applied to map phase transformations in other metallic-glass-forming systems.

In Situ TEM Characterization and Modulation for Phase Engineering of Nanomaterials

“…However, conventional in-furnace heat treatments for structural evolution studies are fragmented and time-consuming, as they need to be conducted on a number of different specimens. The in situ heating TEM approach provides the potential to study the microstructure and composition evolution at the atomic level. − Two-phase Ti-based alloys, consisting of the low-temperature hcp α-phase and the high-temperature bcc β-phase, are widely used in aerospace materials and biomaterials. Through the in situ heating TEM technique, the atomic-scale observation of the nucleation-mediated phase transformation in a Ti–Mo alloy was achieved, as shown in Figure .…”

Nanoscale Heterogeneities of Non-Noble Iron-Based Metallic Glasses toward Efficient Water Oxidation at Industrial-Level Current Densities

“…To address these requirements, MGs (also referred to as amorphous alloys), with several unique characteristics of multicomponents, − structural heterogeneities, − metastable nature, − high atomic diffusion rate, − and so forth, have demonstrated great potential for the discovery and development of novel catalysts . Particularly, it was found that Pd 40 Ni 10 Cu 30 P 20 MGs with their intrinsic chemical heterogeneity present an amazing self-stabilizing behavior that enables them to retain a high efficiency of 100% even after 40,000 s testing in the electrocatalytic process .…”

Boosting Oxygen‐Evolving Activity via Atom‐Stepped Interfaces Architected with Kinetic Frustration

“…This provides a possibility for introducing heterogeneous solid-solution nanocrystals with controllable morphology, grain size, and volume fraction in metallic glass (MG) matrices. [15,16] More importantly, taking advantage of the large glass-forming ability and the unique kinetic frustration effect of transition metal-based MGs during rapid cooling, [17,18] we can readily tune the nucleation and growth of the in situ-formed nanocrystals so that the desirable catalytically active interfaces can be "frozen-in" upon undercooling of the glass-forming metallic liquid. In addition, as a self-supported substrate, MG matrices have also been proven to be beneficial for electrocatalysis due to their unique amorphous active sites, [19][20][21][22] which could further promote the OER activity.…”