Structure and solidification of the (Fe0.75B0.15Si0.1)100-xTax (x=0-2) melts: experiment and machine learning

Fe-B-Si system is a matrix for synthesis of new functional materials with exceptional magnetic and mechanical properties. Progress in this area is associated with the search for optimal doping conditions. This theoretical and experimental study is aimed to address the influence of Ta alloying on the structure of undercooled (Fe0.75B0.15Si0.1)100-xTax (x=0-2) melts, their undercoolability and the processes of structure formation during solidification. Small concentration of Ta complicates standard ab initio and machine learning investigations. We developed a technique for fast and stable training of machine learning interatomic potential (MLIP) in this case and uncovered the structure of the undercooled melts. Molecular dynamic simulations with MLIP showed that at Ta concentration of 1 at.% there is a sharp change in the chemical short-range ordering in the melt associated with a change in the interaction of Ta atoms. This effect leads to a restructuring of the cluster formation in the system. At the same time, our experimental investigation shows that melts with a Ta content of 1 at.% have the greatest tendency to undercoolability. Alloying with Ta promotes the formation of primary crystals of Fe2B, and at a concentration of more than 1.5 at.% Ta, also of FeTaB. Herewith, near 1 at.% Ta, the crystallization of the melt proceeds nontrivially: with the formation of two intermediate metastable phases Fe3B and Fe2Ta Laves phase. Also, the highest tendency to amorphization under conditions of quick quenching is exhibited by a melt with a Ta concentration of 1 at.%. The results not only provide understanding of optimal alloying of Fe-B-Si materials but also promote a machine learning method for numerical design of metallic alloys with a small dopant concentration.Comment: 26 pages, 10 figure

Phase selection and microstructure of slowly solidified Al-Cu-Fe alloys

The search for effective methods to fabricate bulk single-phase quasicrystalline Al-Cu-Fe alloys is currently an important task. Crucial to solving this problem is to understand the mechanisms of phase formation in this system. Here we study the crystallization sequence during solidification as well as the conditions of solid phase formation in slowly solidified Al-Cu-Fe alloys in a wide range of compositions. We have also constructed concentration dependencies of undercoolability by differential thermal analysis method. These experimental results are compared with data on chemical short-range order in the liquid state determined from ab initio molecular dynamic simulations. We observe that the main features of interatomic interaction in the Al-Cu-Fe alloys are similar for both liquid and solid states and they change in the vicinity of i-phase composition. In the concentration region, where the i-phase is formed from the melt, both the undercoolability and the crystallization character depend on the temperature of the melts before cooling. © 2019 Elsevier B.V.This work was supported by supercomputer of IMM UB RAS and computing resources of the federal collective usage center Complex for Simulation and Data Processing for Mega-science Facilities at NRC “Kurchatov Institute” Russian Science Foundation (grant RNF 18-12-00438 ). The experimental study was perfomed using equipment of the Shared Use Centre of Physical and Physicochemical Methods of Analysis and Study of the Properties and Surface Characteristics of Nanostructures, Materials, and Products, UdmFRC UB RAS. AIMD simulations have been carried out using ”Uran” http://ckp.nrcki.ru

Effect of small nickel additions on viscosity of liquid aluminum

© 2019 Elsevier B.V. In this paper the temperature dependences (from liquidus temperature to 1200 °C) of the kinematic viscosity for the liquid aluminum and the Al–Ni alloys with a nickel concentration of 0.027; 0.055; 0.15; 0.50 and 1.0 at.% have been experimentally investigated by means of the oscillating-cup method. For all liquid alloys under studied the temperature dependences of the viscosity within the heating and cooling regimes coincide. In the case of liquid aluminum and melts with a nickel concentration up to 0.50 at.%, inclusively, a deviation of viscosity polytherms from an Arrhenius dependence was found. It has been shown that the increase of the nickel concentration in the melt leads to an increase of the viscosity values

Effect of small nickel additions on viscosity of liquid aluminum

© 2019 Elsevier B.V. In this paper the temperature dependences (from liquidus temperature to 1200 °C) of the kinematic viscosity for the liquid aluminum and the Al–Ni alloys with a nickel concentration of 0.027; 0.055; 0.15; 0.50 and 1.0 at.% have been experimentally investigated by means of the oscillating-cup method. For all liquid alloys under studied the temperature dependences of the viscosity within the heating and cooling regimes coincide. In the case of liquid aluminum and melts with a nickel concentration up to 0.50 at.%, inclusively, a deviation of viscosity polytherms from an Arrhenius dependence was found. It has been shown that the increase of the nickel concentration in the melt leads to an increase of the viscosity values

Crystal structure and properties of polymeric hexaaqua-hexakis-(2-thiobarbiturato)-disamarium(III)

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала

Coordination effects in hydrated manganese(II) 1,3-diethyl-2-thiobarbiturates and their thermal stability

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.Three new complexes of 1,3-diethyl-thiobarbituric acid (HDetba), barbiturate-bridged 2D Mn(II) polymer [Mn(H2O)2(Detba)2] (1), trinuclear [Mn3(H2O)10(Detba)6] (2) and discrete molecular [Mn(H2O)4(Detba)2]·H2O (3) are synthesized and structurally characterized by the X-ray single crystal technique. In 1–3, the Detba− ions are coordinated to Mn(II) only through O atoms with manganese ions in the octahedral environment. In 1, the Mn(II) ion is coordinated by four μ2 bridge Detba− ions and two terminal H2O molecules. In 2, the Mn1 ion is coordinated by three terminal H2O molecules, two terminal and one μ2 bridge Detba− ion, and Mn2 is connected with two μ2-Detba− ions and four H2O molecules. In 3, the Mn(II) ion is coordinated by two terminal Detba− ions and four terminal H2O molecules. There are intermolecular hydrogen bonds O–H⋯O, O–H⋯S in the structures of 1–3 which form the 3D networks. Structure 2 is stabilized by the π–π interaction. The compounds thermal decomposition comprises dehydration steps and the organic ligand oxidation. © 2017 Elsevier Lt