S.M. Voloshko

Corrosion of 2024 alloy after ultrasonic impact cladding with iron

ABSTRACT The iron-containing layers were produced on the 2024 alloy surface using ultrasonic impact treatment (UIT) in the ambient air and argon environment. Multiple high-energy collisions of the pin of Armco-iron by the treated surface induce the iron cladding by means of solid-state welding of Fe dopants and Al substrate. SEM and EDX analysis and microhardness measurements showed a formation of oxide/intermetallic layers, which thickness ranges from 15–20 to 30–35 μm and hardness achieves ∼4 and ∼9 GPa after the argon-UIT and air-UIT processes, respectively. The polarisation tests in 3.5%NaCl medium showed that the layers are characterised by lower corrosion rates and more positive corrosion potentials than those of the original alloy owing to the formation of Alx-Fey intermetallics. The noblest behaviour was registered for the air-UIT-processed 2024 alloy.

The Temperature Dependence of the Atoms Co Diffusion Coefficient in Pt80Co20(111) Alloy

The method of Ionization Spectroscopy is used to study the thermo-induced kinetics of surface segregation of the Pt80Co20(111) alloy components. The temperature dependence of the Co diffusion coefficient in this alloy is determined. It is found that the value of the activation energy for the segregation of Co atoms in the near-surface region is close to the heat of sublimation of pure Co.

Solid-Phase Diffusion Interaction in Multilayer Thin-Film System Cr/Cu/Ni at Pulse Laser Heating

The laser-induced mass transfer in thin-film substrate /Cr/Cu/Ni system is studied by means of Auger Electron Spectroscopy (AES). For the laser-pulse energy values, E = 100-170mJ, the diffusion of Cu atoms into Ni layer and their accumulation within this layer are observed, whereas at E > 170mJ the same is true for Cr atoms. The observed phenomena are explained on the basis of calculated temperature distribution in the system at issue during lased action. Enhanced transfer of Cr atoms towards external surface is observed under the irradiation regimes leading to the melting of intermediate copper layer. Diffusion coefficients of copper and chromium calculated from their surface accumulation show an exponential dependence on the laser-pulse energy. Under laser heating, the diffusion processes are more manifested as compared with those under conventional thermal annealing. This is bound up with higher concentration of nonequilibrium defects generated within the irradiation zone.

Low Temperature Self-Diffusion of Iron in the 56Fe/57Fe Stable-Isotope Thin-Film System

Low-temperature diffusion in thin films of the stable isotopes, 56Fe/57Fe, was studied by applying secondary ion mass spectrometry (SIMS). Processing of the concentration profiles obtained was done by using the Hall – Morabitto “median gradient” method. The bulk and intergrain selfdiffusion coefficients were determined.

Structural and Concentration Heterogeneities during Formation of Silicide Phases in the Thin Film System Ti(5nm)/Ni(24nm)/Si(001)

By the methods of Auger-spectroscopy and mass-spectrometry of secondary ions, small-angle electron diffraction, X-ray and resistometry analyses the solid-state reactions in the Ti(5 nm)/ Ni(24 nm)/Si(001) thin film system at annealing in running nitrogen in the temperature interval of 723 – 1273 К are investigated. Regularities of phase transformations, consistency of solid-state reactions, layer-by-layer redistribution of components during annealing, features of surface morphology during formation of inclusions of silicide phases are established.

The Diffusion Problem of New Phase Inclusion Growth in Bounded Regions of Oversaturated Solid Solution

The Problem of Solving Diffusion Equation with Free Boundary which Appeared during the Modeling of the Spherical Inclusion Formation Process within Spherical Domain Is Examined. the Algorithm and the Software Were Developed on the Basis of the Rothe Method in Combination with the Integral-Equations Method for their Numerically-Analytical Solution. Results of the Calculations Are Illustrated Graphically.

Diffusion Phase Formation in the Cu-Sn Nanofilms System

Processes involved in the structure and phase formation in the thin film systems Sn(4 nm)/Cu(14 nm) and Сu(14 nm)/Sn(8 nm) in the temperature range 130-500 оС were studied using “in situ” electron imaging and Transmission Electron Microscopy methods (TEM). Solubility of Sn α – solid solution Cu-Sn has been determined from the changes in the lattice parameter. This work was performed in the framework of the Swedish Institute supported cooperative research project “Thin metal films – the interplay of structure diffusion and boundaries” (SI dnr 00699/2009).

Diffusion Formation of Silicide Phases in Ni/Si(001) Nanodimensional Film System

Thermally stimulated solid state reactions in the Ni(10 nm)/Si(001) film system that occur under the annealing in the nitrogen ambient were researched by methods of сross-sectional transmission electron microscopy and scanning electron microscope. It was established that NiSi2 formation consists of several steps: a formation of the NiSi polycrystalline silicide thickness of which twice higher initial thickness of Ni layer; prevailed diffusion of Ni atoms out of NiSi into Si substrate according with lattice mechanism and appearing of exceeding vacancies at grain boundaries; a formation of epitaxial NiSi2 nuclei at separate spots of NiSi/Si(001) interface; regular growth of NiSi2 phase inclusions at the expense of NiSi layer “diffusion dissolution”; a formation of NiSi2 spherical inclusions in the lattice of Si matrix and their coalescence.