Cluster-assembled metallic glasses

A bottom-up approach to nanofabricate metallic glasses from metal clusters as building blocks is presented. Considering metallic glasses as a subclass of cluster-assembled materials, the relation between the two lively fields of metal clusters and metallic glasses is pointed out. Deposition of selected clusters or collections of them, generated by state-of-the-art cluster beam sources, could lead to the production of a well-defined amorphous material. In contrast to rapidly quenched glasses where only the composition of the glass can be controlled, in cluster-assembled glasses, one can precisely control the structural building blocks. Comparing properties of glasses with similar compositions but differing in building blocks and therefore different in structure will facilitate the study of structure–property correlation in metallic glasses. This bottom-up method provides a novel alternative path to the synthesis of glassy alloys and will contribute to improving fundamental understanding in the field of metallic glasses. It may even permit the production of glassy materials for alloys that cannot be quenched rapidly enough to circumvent crystallization. Additionally, gaining deeper insight into the parameters governing the structure–property relation in metallic glasses can have a great impact on understanding and design of other cluster-assembled materials

Detection of hidden structures for arbitrary scales in complex physical systems

Recent decades have experienced the discovery of numerous complex materials. At the root of the complexity underlying many of these materials lies a large number of contending atomic- and largerscale configurations. In order to obtain a more detailed understanding of such systems, we need tools that enable the detection of pertinent structures on all spatial and temporal scales. Towards this end, we suggest a new method that applies to both static and dynamic systems which invokes ideas from network analysis and information theory. Our approach efficiently identifies basic unit cells, topological defects, and candidate natural structures. The method is particularly useful where a clear definition of order is lacking, and the identified features may constitute a natural point of departure for further analysis

AlCoNiFeCrTiVx High-Entropy Coatings Prepared by Electron-Beam Cladding

This is a post-peer-review, pre-copyedit version of an article published in "A. D. Pogrebnjak and O. Bondar (eds.), Microstructure and Properties of Micro- and Nanoscale Materials, Films, and Coatings (NAP 2019), Springer Proceedings in Physics 240". The final authenticated version is available online at: https://doi.org/10.1007/978-981-15-1742-6_16.This study reports the investigation of high-entropy coatings obtained by electron-beam cladding in a vacuum of Al-Co-Ni-Fe-Cr-Ti-Vx powder blend on a steel substrate. V was added to the Al-Co-Ni-Fe-Cr-Ti equiatomic system and the effects of this added element on structure, phase composition and microhardness of AlCoNiFeCrTiVx high entropy coatings resulted from electron beam cladding were studied. The AlCoNiFeCrTiV0 coatings consist of two solid solutions with BCC1 and BCC structure with different lattice parameters and a small volume fraction of σ-phase. It was shown that with an increase in V content from x = 0 to x = 1.5, the phase composition of the coatings transforms from two solid solutions to single BCC solid solution and σ-phases of different compositions. The σ-phase volume fraction increased with an increase in the V content. The addition of V to AlCoNiFeCrTi shows the strengthening effect of the AlCoNiFeCrTiV0.5–1.5 coatings and the Vickers hardness increased from 8.4 to 11 GPa. Microhardness of the coatings was affected by the sigma phase. The hardness enhancement can be likely attributed to the effect of solid solution strengthening and to the presence of σ-phase particles in the coating structure

Spatially Resolved Distribution Function and the Medium-Range Order in Metallic Liquid and Glass

The structural description of disordered systems has been a longstanding challenge in physical science. We propose an atomic cluster alignment method to reveal the development of three-dimensional topological ordering in a metallic liquid as it undercools to form a glass. By analyzing molecular dynamic (MD) simulation trajectories of a Cu64.5Zr35.5 alloy, we show that medium-range order (MRO) develops in the liquid as it approaches the glass transition. Specifically, around Cu sites, we observe “Bergman triacontahedron” packing (icosahedron, dodecahedron and icosahedron) that extends out to the fourth shell, forming an interpenetrating backbone network in the glass. The discovery of Bergman-type MRO from our order-mining technique provides unique insights into the topological ordering near the glass transition and the relationship between metallic glasses and quasicrystals