Volume 58, Nº 1-2 (2016)

A composite refractory material with layer structure obtained by the method of pressure diffusion welding of multilayer Ti/Al packets composed of Ti- and Al-foils is studied. The welding temperature of the packets does not exceed 1200 – 1250°C. A layer structure forms in the process of interdiffusion of titanium and aluminum during welding of the packets.

Special features and advantages of metal matrix composites obtained by pulse loading are considered. Examples of effective use of metal matrix composites in various fields of engineering are presented.

Scanning electron microscopy, different methods of electron diffraction, x-ray spectrum microanalysis and x-ray diffraction analysis are used to study the microstructure and crystallography of eutectic chromium carbides in HP40NbTi alloys in as-cast condition and after endurance tests for 2 – 100 h at 1150°C. The morphology and the transformations of the carbides after the high-temperature endurance tests are investigated.

Causes of formation of defects on the internal surface of oil tubes with ends formed by upsetting in SMS Meer hydraulic presses are considered. Interrelated requirements on billets and calibration of the equipment aimed at intensifying the upsetting process in one pass with growth of the wall thickening factor to about 1.85 are formulated.

The process of formation of graphene layers on a copper substrate is studied as a function of the pressure in the growth chamber. It is shown that the graphene layers form by nucleation and growth of graphene nuclei that later combine into a continuous layer. Growth in the pressure is accompanied by thickening of the synthesized graphene, intensification of compressive stresses, and appearance of structure defects.

Effects of various factors such as the grain size, the morphology of nonmetallic inclusions, and joint microalloying with boron and titanium on the high-temperature ductility of pipe steels are studied. Physical modeling of the conditions of cooling of the skin of a continuous-cast preform in the zone of secondary cooling in a Gleeble facility is performed. Technical recommendations are given for raising the hot ductility of steels under industrial conditions.

Low-carbon martensitic steels (LCMS) 15Kh2G2NMFB and 27Kh2G2NMFB are studied after an isothermal hold at 360°C and 340°C, respectively, with subsequent continuous cooling in air. The temperature and ranges of the dominant shear and diffusion mechanisms of the γ → α transformations are determined by computation. The principal differences in the morphology and the sizes of laths and packets of low-carbon martensite and upper bainite are determined.

Low-carbon martensitic steels (LMS) susceptible to inheritance of structure are considered. The strength, ductility, toughness characteristics, fracture energy, grain structure of the austenite, and micro- and fine structures of heat treated LMS are studied. The formation and decomposition of the austenite is investigated by the method of differential scanning calorimetry (DSC). True strain diagrams and models are designed. Expressions relating the stresses and strains in the stages of uniform and lumped deformation are suggested, and the power criteria for tension and fraction of the LMS are computed.

Relations between the parameters of dynamic crack resistance, impact toughness, sizes of zones of plastic strain in the start region, hardness of the unstrained material, strength characteristics, and tempering temperature of steel 09G2S are determined. The linear regression equations are used to construct mathematical and graphical models for predicting the level of properties in quenched and tempered steel 09G2S. The method is used to predict the properties of a tubular billet from steel 09G2S with composition somewhat different from the rated one after quenching and high tempering at 570°C.

Steel 24Kh2G2NMFB is studied after carburizing and different heat treatments. The hardness and microhardness of the surface layer and of the matrix are measured. The content of retained austenite is determined by the method of x-ray diffraction analysis. Heat treatment modes improving the structure of the surface layer after carburizing are suggested.

The principal possibility of formation of a structure of lower carbide-free bainite under long-term holds is shown for steels of two alloying systems Kh3G3MFS and KhN3MFS containing 0.25 – 0.30 and 0.40 – 0.45% carbon. Dilatometric analysis of the phase transformations is performed and the bainitic range of the diagrams of decomposition of supercooled austenite is plotted. The structure is studied by the methods of light, scanning electron, and transmission microscopy.