卷 57, 编号 9-10 (2016)

Variants of initiation of growth of crystals of α-martensite by couples of elastic waves propagating in directions <001>_γ and <110>_γ in singles crystals of Fe31Ni are suggested. The dynamic theory is used to show that the expected orientations of habit planes {110}_γ, {001}_γ and {559}_γ differ from the typical {31015}_γ. Possible features of tetragonality of martensite crystals are discussed. The power of the sources of ultrasound required for initiation of γ – α martensitic transformation is estimated.

Adiagram of transformations in low-alloy boron-containing steel B27 with high resistance to abrasive wear is plotted under continuous cooling. Chemical, metallographic and dilatometric analyses are performed, and the hardness of the steel is measured. Continuous cooling curves are obtained from the temperature of austenitization at a rate of 0.17 – 25 K/sec in the temperature range of 800 – 500°C.

Shape memory alloy Fe – 14Mn – 6Si – 9Cr – 5Ni (wt.%) obtained by cold pressing and sintering of a mixture of powder elements or of mechanically alloyed powder is studied. To compact the alloy additionally the specimens are subjected to hot rolling. Solution treatment of different duration (0.6 – 4.8 ksec) at 1473 K in low vacuum, nitrogen or argon is performed. The structure of the alloy after such treatments is studied by the methods of x-ray diffraction and optical and scanning electron microscopy.

Results of a study of the effect of the parameters of electroerosion treatment in a GF Agie Charmilles CUT 1000 OilTech wire-cutting bench on the size accuracy, the quality of the surface layer of cuts, and the microstructure of the surface of the treated parts are presented.

A method of ultrafast deposition of hard-alloy coatings from powders upon passage of a powerful pulse of electric current is considered. The structure of the coatings obtained by the electric-pulse and standard processes is studied by metallographic, electron microscope and x-ray diffraction analyses. The physical, mechanical and cutting properties of the hard-alloy coatings are determined. The endurance of the cutting tools with hard-alloy coatings is estimated under the conditions of large-scale and pilot productions. The possibility of creation of tools with enhanced operating characteristics is demonstrated.

The structure and properties of a quenched chromium-base alloy are studied after different modes of tempering. The Hollomon parameter is determined and shown to be applicable to alloys, the structure and properties of which after changing the temperature and time of the heat treatment is determined by diffusion of metal atoms in a substitutional solid solution. In the case of constancy of the Hollomon parameter the temperature and time regimes of the tempering provide identical structures and properties.

Thermochemical treatment of a hard alloy is implemented by alloying its surface with the help of a low-energy strong-current electron beam prior to depositing a wear-resistant coating. The method increases substantially the service life of the tool. The laws of formation of refractory compounds in the surface layer due to initiation of a reaction of self-propagating high-temperature synthesis in the mode of thermal explosion are determined. The change in the wear behavior of the modified tools is studied.

Possibilities of control of the level of accumulated damage in dies for cold and hot forming as a function of the coercivity are considered. The coercivity of the material of dies for hot forging and cold stamping is studied. Formulas are obtained for determining the coercivity in steels for hot die forging in the state as delivered.

Special features of a recent metallurgical process for structural steels are considered. The types of nonmetallic inclusions, precipitates of excess phases and impurities are described, and the effect of their content, size, morphology and volume distribution on the production, operational and quality characteristics of the steel is determined. Specific examples are used to show the perspectives of the formulated principle for advancing the combination of properties of structural steels of various types at substantial decrease in the expenses.

The effect of pit and intergrain corrosion on the mechanical properties (strength and ductility) and inhomogeneity of the fields of plastic strain in grains is determined experimentally. The parameters of the laws of distribution of the principal strains and their intensities under uniaxial tension of specimens are determined. The values of the stress-strain state parameter are obtained and the correlation relations between the strains in individual crystallites are estimated after different corrosion impacts on specimens of steel 08Kh18N10T.

Video recording of the free recovery of “hot shape” (typical for the austenitic domain) in shape-memory alloy Fe – 28% Mn – 6% Si – 5% Cr during heating of specimens with a “cold shape” typical for the martensitic domain is performed. Prior to each measurement the specimens are deformed by caliber bending at room temperature in martensitic condition. The thermomechanical training consists in 10 cycles of bending – heating – cooling. Displacements of the free ends of the specimens are plotted as a function of the temperature and the plots are used to determine the critical temperatures of the reverse martensitic transformation.

The morphology of the structure of the near-weld region of the heat-affected zone of welded joints of high-strength pipe steels is studied and its effect on the resistance of the metal to brittle fracture is determined.

A concept of intense plastic deformation is suggested. Schemes for molding cylindrical powder billets with simultaneous refinement of their structure adaptable to pressing in industrial presses are discussed. Formulas for calculating the expedient pressures in the compacted powder billets and for determining the strain accumulated under the schemes suggested are presented.

The aspects of terminology, definitions and classification in the technology of additive production are considered. The principal possibility of fabrication of complex-shape parts from a refractory cobalt alloy by the method of selective laser melting and deposition of hard and wear-resistant coatings from Ti and SiC powders by coaxial laser surfacing is shown. The technological possibility of microlaser surfacing with lateral resolution about 100 μm in the production of parts from aluminum alloys is considered. The mechanisms of formation of structure in the studied alloys typical for selective laser melting, laser surfacing and microlaser surfacing are determined. The physical and mechanical properties of the alloys are investigated.