Effect of electron-beam melting upon the properties of grade ShKh15 ball-bearing steel

Summary Electron-beam melting reduces the gas content, harmful impurities and nonmetallic inclusions in ShKh15 steel, thus leading to a considerable improvement in its physical, mechanical, and electrochemical properties. Most marked is the improvement in the resistance of the steel to cyclic loads: its fatigue limit is increased by 33% to a level higher than that recorded for any steel of this class in the USSR and abroad. Compared with electro-slag and vacuum-arcmelted steels, the electron-beam-melted grade has higher fatigue strength, higher UTS under conditions leading to hydrogen embrittlement, and higher resistance to corrosion.     

Nested self-similar wrinkling patterns in skins

Stiff thin films on soft substrates are both ancient and commonplace in nature; for instance, animal skin comprises a stiff epidermis attached to a soft dermis. Although more recent and rare, artificial skins are increasingly used in a broad range of applications, including flexible electronics, tunable diffraction gratings, force spectroscopy in cells, modern metrology methods, and other devices. Here we show that model elastomeric artificial skins wrinkle in a hierarchical pattern consisting of self-similar buckles extending over five orders of magnitude in length scale, ranging from a few nanometres to a few millimetres. We provide a mechanism for the formation of this hierarchical wrinkling pattern, and quantify our experimental findings with both computations and a simple scaling theory. This allows us to harness the substrates for applications. In particular, we show how to use the multigeneration-wrinkled substrate for separating particles based on their size, while simultaneously forming linear chains of monodisperse particles.     

Thermal stability of MoSi<Subscript>2</Subscript>-SiC composites in air at temperatures of 1100–1400°C

Composites xMoSi₂-(100 ? x)SiC are prepared over a wide composition range (x= 10–90 mol %) by hot and cold pressing methods. The optimum pressing parameters (temperature, pressure, time) are determined. The heat resistance, the thermal stability, the porosity, and the phase composition of the composites are investigated after heat treatment for 100 h in an air atmosphere. Comparative data on the heat resistance and the porosity of the composites are analyzed as a function of the composition, the temperature (1100, 1400°C), and the preparation technique. The range of optimum compositions of the materials characterized by a low porosity and a high thermal stability is established.     

Investigation into the surface morphology of nanosized silicate and hybrid films by optical and atomic-force microscopy

This paper reports on the results of investigations into the surface morphology of hybrid organic-inorganic films prepared by the sol-gel method on single-crystal semiconductor silicon. The spin-on-glass films are coated from sols based on tetraethoxysilane. The chemical composition of the films is modified by introducing inorganic compounds (dopants), namely, boric acid and gadolinium nitrate, into the sols. For the purpose of increasing the film thickness, the sols are modified by small amounts (～1 wt %) of polyols that have linear and branched structures, different molecular weights, and different numbers of active functional groups. A substantial change in the surface morphology of the spin-coated films, i.e., the formation of a specific structure of the films under the action of the above dopants and modifiers, is revealed using optical and atomic-force microscopy.     

Kinetics of accumulation of scattered damage in polycrystalline materials with various grain sizes under small-scale strain conditions

The paper addresses damage accumulation processes that occur during static deformation in steels 45 and 09G2S and in brass L63 in the initial state and upon “grain annealing.” The authors discuss new experimental evidence on the damage accumulation kinetics during deformation of polycrystalline materials that differ in nature and grain size, including materials in the unloaded state and those under stresses, with small and very small strains (0.05–0.15%). The results obtained have been the necessary physically consistent explanations. Analytical approximations of the correlation between the main mechanical properties of materials (hardness, yield stress, and ultimate strength) and their structure parameters (grain size) are given.