A.V. Panin

Mesoscopic surface folding in EK-181 steel polycrystals under uniaxial tension

The work is experimental and theoretical study of folded structures formed on free surfaces of polycrystalline materials under uniaxial tension. General mechanisms by which the folded deformation relief develops are demonstrated with the example of EK-181 steel. Numerical simulation shows that the polycrystalline structure of the material can be a condition responsible for local curvature of its initially flat surface and hence for periodic distribution of normal tensile and compressive stresses.

Fractal analysis of electromigration-induced changes of surface topography in Au conductor lines

Evolution of surface morphology of Au conductor lines under high-density electric current is studied by scanning tunneling microscopy. The loss of conductivity of thin Au films is found to occur through formation of voids resulted from electromigration followed by the depletion of the material. It is shown that the density of electric current passing through thin conducting films greatly affects their lifetime. Fractal analysis is employed to estimate numerically changes of surface topography of Au films. The fractal dimension is shown to be an optimum prefracture criterion for thin metal films under applying electric current.

Role of local nanostructural states in plastic deformation and fracture of solids

The paper substantiates the concept of physical mesomechanics that the basis for nonlinear behavior of solids under plastic deformation and fracture is the formation of nanostructural states in local highly nonequilibrium zones. Their structural transformations and two-phase decay govern the generation of strain-induced defects and cracks. Nonlinear wave mechanisms of nanostructural states influence on plastic deformation and fracture are discussed.

Nonlinear wave processes in a deformable solid as a hierarchically organized system

Theoretical predictions and experiments demonstrate that solid state mechanics should consider, along with a structurally equilibrium 3D crystalline subsystem, a structurally nonequilibrium planar subsystem as a complex of all surface layers and internal interfaces with broken translation invariance. Primary plastic flow of a loaded solid develops in its structurally nonequilibrium planar subsystem as channeled nonlinear waves of local structural transformations that determine the self-organization law of multiscale plastic flow. These waves initiate mesoscale rotational deformation modes, giving rise to all types of microscale strain-induced defects in the planar subsystem. The strain-induced defects are emitted into the crystalline subsystem as an inhibitor of nonlinear waves of plastic flow in the planar subsystem. Plastic deformation of solids, whatever the loading type, evolves in the field of rotational couple forces. Loss of hierarchical self-consistency by rotational deformation modes culminates in fracture of material as an uncompensated rotational deformation mode on the macroscale.

Surface modification of structural materials by low-energy high-current pulsed electron beam treatment

Microstructure formation in surface layers of pure titanium and ferritic-martensitic steel subjected to electron beam treatment is studied. It is shown that low energy high-current pulsed electron beam irradiation leads to the martensite structure within the surface layer of pure titanium. Contrary, the columnar ferrite grains grow during solidification of ferritic-martensitic steel. The effect of electron beam energy density on the surface morphology and microstructure of the irradiated metals is demonstrated.

The effect of laser treatment of WC-Co coatings on their failure under thermal cycling

The given paper studies the effect of surface laser treatment of WC-Co coatings on their surface morphology, phase composition and thermal cycling behavior. The coatings were sprayed on stainless steel substrates with the use of a high velocity oxy fuel spraying process. Application of the scanning electron microscopy and X-ray diffraction showed that re-melting of the coating surface layer during laser treatment induced changes in its phase composition as well as the formation of regular rows of globular asperities on the coating surface. The latter resulted in a sharp increase in thermal shock resistance of the laser treated WC-Co coatings under water quench tests; its underlying mechanism are proposed and discussed in the paper.

Fracture toughness and oxidation resistance of Ti-Al-N coatings on stainless steel substrates

The effect of preliminary ion bombardment of a stainless steel substrate on the fracture toughness and oxidation resistance of Ti-Al-N coatings was studied using scanning and transmission electron microscopy, X-ray diffraction and nanoindentation. The ion-beam treatment of the substrate was shown to substantially affect the microstructure and the hardness of the coatings as well as to improve their fracture toughness estimated from scratch tests. In addition, it resulted in higher oxidation resistance of the Ti-Al-N coatings under thermal cycling.

Magnetic and Mechanical Properties of Deformed Iron Nitride γ′ -Fe4N

The present study is aimed at magnetic and mechanical properties of iron nitride (-Fe4N) with elastic deformation. Electronic structure and thermal properties of the iron nitride are also studied to have a comprehensive understanding of the characteristics of -Fe4N. This study is focused on the variation of the magnetic and the mechanical properties of iron nitride with a change in crystal size represented by lattice constant. As the lattice constant is altered with deformation, magnetic moment of Fe-II atoms is appreciably elevated, while that of Fe-I atoms is nearly unchanged. Dependence of the magnetic moment and the bulk modulus on the lattice constant is examined. Meanwhile, chemical bonds between Fe atoms and N atoms formed across the crystal have been visualized by delocalization of atomic charge density in electron density map, and thermodynamic properties, including entropy, enthalpy, free energy, and heat capacity, are evaluated.

Microstructure and mechanical properties of CP-Ti subjected to UIT

The ultrasonic impact treatment (UIT) effect on microstructure and mechanical properties of commercial purity titanium (CP-Ti) was studied. The microstrucrure was investigated by X-ray diffraction analysis and optical profilometer New View 6200. The microhardness of CP-Ti specimens was measured by microhardness tester with the Vickers pyramid. It was found that UIT of CP-Ti specimens led to severe plastic deformation of surface layer with a thickness equals to 120 μm. This was accompanied by an increase in compressive residual stresses, a growth of the microhardness, a crystallographic texture change and a rise of density of deformation twins in surface layers of titanium specimens. It was shown that the deformation twins play a determining role in microstructure and mechanical properties changes of the surface layer of titanium specimens.

Improvement of the wear resistance of electroplated Au-Ni coatings by Zr ion bombardment of Ni-B sublayer

The effect of bombardment of the Ni-B sublayer by Zr ion beams on the surface morphology and tribomechanical properties of Au-Ni coatings was investigated. It was found that the treatment has no significant effect on the surface roughness and grain size of the Au-Ni coatings, while it provides essential reducing of their friction coefficient and improvement of wear resistance. It is shown that increased wear resistance of these coatings was caused by their strain hardening resulted from localization of plastic strain. The optimal Zr fluence were determined that provide the maximum reduction of linear wear of the coatings.