Showing papers in "Metal Science and Heat Treatment in 1994"
TL;DR: In this article, the effect of scandium content on the structure and properties of pressed strips and cold-rolled sheets of alloy Al-5.5% Zn-2.0% Mg was investigated.
Abstract: Commercial weldable aluminum alloys additionally containing scandium have recently been developed in Russia: thermally nonhardening alloys based on the system Al-Mg (01570, 01523, 01515), and thermally hardening alloys based on the systems-Al-Zn-Mg (01970, 01975) and Al-Mg-Li (01421, 01423). Compared with other weldable aluminum alloys these materials exhibit improved operating properties. This is achieved as a result of a small addition of scandium which displays a high modifying effect and it promotes retention of an unrecrystallized structure for alloys. Results are presented in this article for a study of the effect of scandium content on the structure and properties of pressed strips and cold-rolled sheets of alloy Al-5.5% Zn-2.0% Mg.
16 citations
TL;DR: In this paper, the authors investigated the possibility of improving the tribotechnical characteristics and corrosion resistance of the widely known aluminum alloys PV-90, D16, and 1420 using the titanium nitride coatings applied by the ionplasma method.
Abstract: The creation of a titanium nitride coating on the surface of articles is one of the most effective methods of enhancing the wear resistance of materials. This coating is also promising from the standpoint of the possibility of achieving high hardness, strength, and simultaneously good protective-and-decorative surface properties. We investigated the possibility of improving the tribotechnical characteristics and corrosion resistance of the widely known aluminum alloys PV-90, D16, and 1420 using the titanium nitride coatings applied by the ionplasma method.
10 citations
TL;DR: In this paper, internal nitriding is considered as a particular case of material dispersion strengthening, accompanied by preparation of a heterophase structure of a diffusion layer: the matrix is a solid solution with fine particles of alloying element nitride particles distributed within it.
Abstract: Internal nitriding, as for internal oxidation, may be considered as a particular case of material dispersion strengthening. Internal nitriding is accompanied by preparation of a heterophase structure of a diffusion layer: The matrix is a solid solution with fine particles of alloying element nitride particles distributed within it. Internal nitriding may be special importance as a version of dispersion hardening for high-temperature alloys. Possibilities are considered in this article for internal nitriding of cobalt alloys.
5 citations
TL;DR: Internal nitriding is a process of surface saturation with nitrogen, in which there forms a diffusion layer, consisting of nitride particles that are uniformly distributed in a solid solution but without a surface zone of continuous nitrides, as in conventional Nitriding.
Abstract: Internal nitriding is a process of surface saturation with nitrogen, in which there forms a diffusion layer, consisting of nitride particles that are uniformly distributed in a solid solution but without a surface zone of continuous nitrides, as in conventional nitriding. This is achieved by selection of the alloy chemical composition and the nitriding process regimes. The presence of this diffusion layer opens up broad possibilities for the hardening of various alloys, since a high level of brittleness of the layer is avoided. This is an advantage over conventional nitriding.
4 citations
TL;DR: In this article, stable and metastable phase diagrams for alloys with shape mennory based on intennetallic phases with the crystalline structures B2, DO3, L21 are presented.
Abstract: In the alloys of the systems Ni-Ti, Cu-Al-Ni, Cu-Zn-Al, Cu-Al-Mn shape memory is found in small intervals of concentration of the existence of intennetallic phases with the crystalline structures B2, DO3, L21 A deviation from the optimal range of concentrations or the segregation of phases in heat treatment impairs the characteristics of shape restoration In the elaboration and introduction of alloys with shape mennory based on intennetallic phases it is therefore particularly important to study stable and metastable phase diagrams The plotting of such diagrams is the main task of the present work
3 citations
TL;DR: In this paper, the effect of laser radiation on the mechanical properties of the indicated components was studied and local laser heating was used to reduce the deformation and increased brittleness of the components.
Abstract: Steel 20KhN2M is used for the production of gears and other components, for whose service enhanced wear resistance is required in retaining resistance to impact loadings. The deformation (warping) and increased brittleness of these components are observed after their bulk hardening. The deformation of the components cannot be completely eliminated, even on hardening with the use of superhigh frequency, radiation. Local laser heating lowers deformation to a significant degree. In this connection. it was interesting to study the effect of laser radiation on the mechanical properties of the indicated components.
3 citations
TL;DR: In this paper, the effect of microalloying with some rare-earth metals (La, Dy, Y, Ce) on the amount of β phase, the mechanical properties at 20°C, the creep-rupture structure, and creep at 600°C of VT18U high-temperature titanium alloy was studied.
Abstract: A study has been made of the effect of microalloying with some rare-earth metals (La, Dy, Y, Ce) on the amount ofβ phase, the mechanical properties at 20°C, the creep-rupture structure, and creep at 600°C of VT18U high-temperature titanium alloy.
3 citations
TL;DR: In this paper, a review of the application of new technologies of hardening the surface of alloys on the basis of spontaneously propagating high-temperature synthesis (SHS) is presented.
Abstract: The discovery in 1967 of the phenomenon of the propagation of the combustion front of powdered high melting chemical elements, which leads to the formation of high melting compounds, marked the beginning of the application of new technologies of hardening the surface of alloys on the basis of spontaneously propagating high-temperature synthesis (SHS). In dependence on the conditions of realizing SHS processes it is possible to obtain diffusion layers in the regime of combustion or thermal self-ignition. The article reviews these methods on the example of chrornizing of carbon steels. The microstructure, phase and chemical composition of the coatings were investigated. The obtained chrornized layers are very heat-resistant and have great microhardness.
3 citations
TL;DR: In this article, the authors present the results of investigations which form the basis for development of high-strength weldable bainite steels obtained using in-line thermomechanical treatment in the rolling mill and not requiring heat treatment with special heating.
Abstract: In this paper, we present the results of investigations which form the basis for development of high-strength weldable bainite steels obtained using in-line thermomechanical treatment in the rolling mill and not requiring heat treatment with special heating. The thennomechanical treatment involves controlled rolling followed by regulated cooling. In order to achieve high strength properties than in steels with ferrite—pearlite structure, the alloying and cooling conditions for rolling in the thermomechanical treatment cycle must ensure that lowtemperature austenite transformation products be obtained with a fine original austenite grain.
3 citations
TL;DR: In this article, the influence of conditions of glow-discharge nitriding of tantalum and the alloy Ta-10% W on the microhardness and phase composition of the diffusion layer is discussed.
Abstract: Many methods are used to harden tantalum (solid-solution hardening, plastic deformation, grain ordering, dispersion hardening, and introduction of hardening dispersion phases in the form of particles, filaments, whiskers, fibers, etc.). The influence of conditions of glow-discharge nitriding of tantalum and the alloy Ta-10% W on the microhardness and phase composition of the diffusion layer is discussed.
3 citations
TL;DR: In this article, the authors evaluated the resistance to crack generation and development for wrought medium-strength aluminum alloys AMg6, AK4-1, and high-strength alloy V96ts.
Abstract: Crack resistance is an important characteristic of the structural strength of materials. The reliability criteria for articles depend upon it, i.e., ‘safe damage’ and ‘safe life.’ The first criterion is governed by the capacity of a material to provide article operation in the presence of cracks, and the second is governed by the time to generation of the first crack. Thus in order to evaluate crack resistance it is necessary to determine material resistance to crack generation and development. In this work resistance to crack generation and development is evaluated for wrought medium-strength aluminum alloys AMg6, AK4-1, and high-strength alloy V96ts which has a matrix (pseudo-single-phase) structure.
TL;DR: In this paper, the authors considered the technology for combination surface hardening of low carbon steel, involving laser alloying of the surface with nitride forming elements followed by nitriding of the entire alloyed layer.
Abstract: In recent years, combination methods for surface hardening of alloys have been actively developed and incorporated into industrial practice. The widespread interest in such technologies is explained by the possibility of obtaining extremely high-quality surface properties for the pieces. In this paper, we consider the technology for combination surface hardening of low-carbon steel, involving laser alloying of the surface with nitride forming elements followed by nitriding of the entire alloyed layer. We have investigated the properties of the hardened surface layer.
TL;DR: In this article, the common characteristics of fracture and crystallization processes are analyzed from the point of view of phase transition theory, and the characteristic features of the generation and accumulation of defects, and also nucleation of crystals of new phase are considered.
Abstract: Recently in many areas of science we have seen increasing interest in critical phenomena, phase transitions, and the common characteristics of various processes. However, common characteristics have not been determined connecting processes of deformation, fracture, and crystallization. Obviously, the common nature of these processes, as for many other natural phenomena, should be sought on the basis of the thermodynamics of irreversible processes. Such an approach probably will allow us to connect phenomena occurring in solid, liquid, and gaseous media. This paper is devoted to analysis of the common characteristics of fracture and crystallization processes. We consider the characteristic features of the generation and accumulation of defects, and also nucleation of crystals of new phase. Both processes (fracture and crystallization) are analyzed from the standpoint of phase transition theory.
TL;DR: In this article, features of the thermal fatigue failure mechanism for steels 3Kh2V8F and 4Kh5MFS used for mold manufacture are considered. But the authors do not consider the effect of thermal fatigue on the operating surface layer of a mold.
Abstract: Extensive use of die casting is limited by the short operating life of molds with cyclically changing temperature and stresses. As a result of this action there is thermal fatigue failure of the operating surface layer of a mold. This article considers features of the thermal fatigue failure mechanism for steels 3Kh2V8F and 4Kh5MFS used for mold manufacture.
TL;DR: In this paper, a method of impact bending test is proposed to evaluate the actual strength of gear teeth, which can be used to estimate the hardness and wear resistance of gear wheels with relatively ductile cores.
Abstract: Chemicothermal treatment processes are widely used in engineering to improve the working lives of important components, of which the most common is nitrocementation. That process has been applied at the Volga Automobile Plant mainly to sprockets in gear transmissions, which need high hardness and wear resistance in the surfaces with relatively ductile cores. Although various forms of chemicothermal treatment are widely used, there has been no universal method of evaluating the strengths of gear wheels. Standard methods of estimating strength (σu, σt, σb, and hardness) have a major shortcoming: They can determine only the characteristics of the cores for case-hardened materials. Here we consider a method of impact bending test, which enables one to evaluate the actual strength of gear teeth.
TL;DR: In this paper, the authors investigated the relations of magnetic and dislocational hysteretic mechanisms of energy dissipation of vibrations in the hertz frequency range and in a broad temperature range, and also investigated the conditions of attaining a stable highly damping state of high chromium ferritic steels.
Abstract: The level of the magnetoelastic properties and their stability in a wide range of temperature and strain effects are determined by the combination of various bysteretic and relaxational mechanisms of energy dissipation in the material. The design of corrosion-resistant steels based on the system Fe-Cr with high stability and good damping ability is a complex practical problem. The aim of the present work is to investigate the relations of magnetic and dislocational hysteretic mechanisms of energy dissipation of vibrations in the hertz frequency range and in a broad temperature range, and also to investigate the conditions of attaining a stable highly damping state of high chromium ferritic steels.
TL;DR: In this article, the effect of the base (Mo, Cr), alloying (V Nb, Fe, W, Ti), and impurity (C, Si, P, Fe) elements on phase and structural transformations in Ni-Mo and Ni-Cr alloys are considered.
Abstract: In this article the effect of the base (Mo, Cr), alloying (V Nb, Fe, W, Ti), and impurity (C, Si, P, Fe) elements on phase and structural transformations in Ni-Mo and Ni-Cr alloys are considered. Their corrosion and electrochemical behavior, and mechanical properties after various heat treatments related to commercial practice or the conditions of use are reviewed. Based on the regularities observed, general rules are formulated for the development of corrosion-resistant, deformable, and weldable nickel-base alloys with a required combination of properties.
TL;DR: A magnetically soft iron-base alloy in the form of ribbon with an amorphous-crystalline structure was developed and studied as discussed by the authors, and magnetic heads were fabricated using the amorphized-crystaline alloy with which it was possible to increase the informational capacity, speed and service life of external memory devices for electronic computers.
Abstract: A magnetically soft iron-base alloy in the form of ribbon with an amorphous-crystalline structure was developed and studied. The magnetic properties of this alloy are superior to those of purely amorphous alloys designated for the same use, which, moreover, contain 80% of the expensive metal cobalt. Magnetic heads were fabricated using the amorphous-crystalline alloy with which it was possible to increase the informational capacity, speed, and service life of external memory devices for electronic computers.
TL;DR: The martensitic transformation is a special form of phase transformation that is not associated with the conventional temperature-dependent parameters: the number of centers and the crystal growth rate as mentioned in this paper, and the internal stresses are important for this transformation.
Abstract: The martensitic transformation is a special form of phase transformation that is not associated with the conventional temperature-dependent parameters: the number of centers and the crystal growth rate. The internal stresses are important for this transformation. How can we define the martensitic transformation? Possibly as follows: “The martensitic transformation is a diffusionless phase transformation that is induced by the stresses.” The stream of studies devoted to the martensitic transformation is not abating, and each author often has his own point of view. But they all contribute very little to clarification of the nature of this phenomenon and, unfortunately, even less to their use in practice; for example, for regulation of the kinetics of the transformation. We shall present two articles that are devoted to the profound causes and subtle characteristics of the martensitic transformation.
TL;DR: In this article, the effect of grain size on the structure and contact durability of nitrided steel was evaluated, and it was shown that grain size no greater than No. 8 in the billets is necessary to achieve higher serviceability.
Abstract: The austenite grain size in forgings and rolled stock used for the production of medium-size and large nitrided toothed gears is No. 5–7, depending upon the grade of the steel. Practical experience has shown that it is necessary to obtain a grain size no greater than No. 8 in the billets in order to achieve the higher serviceability in gears of this type. No information is available concerning the utility of fisrther reducing the grain size of nitriding steels. In view of this, the effect of austenite grain size on the structure and contact durability of nitrided steel was evaluated.
TL;DR: In this article, the effect of rapid tempering on the properties of steel 30KhGSA was investigated and it was recommended that during traditional heat treatment low-temperature (200-250 °C) and high-tem temperature (550-600°C) tempering is used which may not always provide the optimum combination of strength and ductility properties.
Abstract: The phenomenon of first-order temper brittleness, which is defined by a reduction in impact strength, by an increase in the ductile-brittle transition temperature, and by an increase in the proportion of the brittle component in a fracture, is observed in steels after tempering in the range 350–500°C. For steels inclined toward temper brittleness, it is recommended that during traditional heat treatment low-temperature (200–250 °C) and high-temperature (550–600°C) tempering is used which may not always provide the optimum combination of strength and ductility properties. Features are considered in the present work for the effect of rapid tempering on the properties of steel 30KhGSA.
TL;DR: In this article, the authors studied the distinctive features of primary recrystallization in semi-finished alloy 1570 strip and showed that the data from metallographic analysis of the primary re-stallization of Alloy 1570 are inadequate in comparison with the data for its industrial analog, Alloy AMg6.
Abstract: The study of primary recrystallization processes in deformable aluminum alloys that have not been hardened by heat treatment makes possible a substantiated choice of technological conditions for pressure shaping. The data from metallographic analysis of the primary recrystallization of alloy 1570 are inadequate in comparison with the data for its industrial analog, alloy AMg6. In view of this we studied the distinctive features of primary recrystallization in semi finished alloy 1570 strip.
TL;DR: In this article, the authors determined the laws governing the reaction of titanium with those gases during CHT in a nitrogen medium, including carbon dioxide, oxygen, water vapor, and carbon dioxide.
Abstract: Nitrogen gas used in industry as an active medium for chemical heat treatment (CHT) of metals, including titanium, containing impurities, the main ones being oxygen, water vapor, and carbon dioxide The aim of this study is to determine the laws governing the reaction of titanium with those gases during CHT in a nitrogen medium
TL;DR: In this paper, the authors investigated the effect of the amount of residual austenite in the melted layer on the wear resistance, the contact fatigue, and the anodic dissolution from some steels and pig irons.
Abstract: After melting the thin surface layer of steels and pig irons with a localized heat source, the amount of residual austenite in this layer is determined by the degree of dissolution of the carbide phase and correlated with the maximum temperature attained at the end of the heating stage. In this work, we have investigated the effect of the amount of residual austenite in the melted layer on the wear resistance, the contact fatigue, and the anodic dissolution from some steels and pig irons.
TL;DR: In this article, the structure of low and medium carbon structural steels after surface alloying using laser heating was investigated and the results showed that the structure can be improved by using a laser heating method.
Abstract: In recent years, laser radiation has been increasingly used for surface treatment of machine and tool parts. In cases when laser technologies can be cost-competitive, they have begun to displace traditional treatment methods. In this paper, we consider the structure of low- and medium-carbon structural steels after surface alloying using laser heating.
TL;DR: In this paper, the structure of single crystals of an intermetallide, the composition of which is close to stoichiometric, was investigated and it was shown that it is sensitive to microadditions of rare-earth metals within limits of 0.05-0.3% and crystallization rate of 10-210 mm/min.
Abstract: The structure of single crystals of an intermetallide, the composition of which is close to stoichiometric, was investigated. It was shown that it is sensitive to microadditions of rare-earth metals within limits of 0.05–0.3% and crystallization rate of 10–210 mm/min.
TL;DR: In this paper, the structural formation of the surface layers of the titanium alloy VT3-1 during laser alloying from dross coatings containing a mixture of boron carbide B4C and chromium was investigated.
Abstract: The low wear resistance of titanium and its alloys limits their use in machine building. Methods for the surface hardening of titanium and its alloys, which tend to enhance their antifriction properties. are of significant interest in this respect. Laser alloying is one of the most promising methods of improving the strength of the surface. In this study. we investigated the characteristic features of the structural formation of the surface layers of titanium alloy VT3-1 during laser alloying from dross coatings containing a mixture of boron carbide B4C and chromium.
TL;DR: The incorrect treatment of such concepts as dissipative structure, kinetic nonequilibrium phase transition, open system, and others that apply to the hypercritical region of self-organizing structures is permitted by a number of authors, whereas deformation with its evolution of the dislocation system corresponds to the hypocritical region of a closed system with increasing configuration entropy.
Abstract: Use of assumptions concerning synergetics and self-organization in a number of studies on the deformation, strength, and failure of metals makes it possible to determine a correct approach to the nature of these phenomena. The incorrect treatment of such concepts as dissipative structure, kinetic nonequilibrium phase transition, open system, and others that apply to the hypercritical region of self-organizing structures is permitted by a number of authors, whereas deformation with its evolution of the dislocation system corresponds to the hypocritical region of a closed system with increasing configuration entropy, where the formation of a dissipative structure is excluded.
TL;DR: In this article, the influence of oxygen on the structure and properties of a titanium nitride-base coating on an R18 steel base was investigated and a method of application of a Titanium nitride base coating with optimum service properties on a tool was proposed.
Abstract: In application of titanium nitride-base coatings entry of oxygen into them is possible with use of low purity nitrogen or with insufficient vacuum. In service during heating in air oxygen also reacts with the coating material. In this work the influence of oxygen on the structure and properties of a titanium nitride-base coating on an R18 steel base was investigated. A method of application of a titanium nitride-base coating with optimum service properties on a tool is proposed.
TL;DR: In this article, the use of casehardening (CH) techniques to increase hardness and corrosion resistance and lower the surface roughness of various components and tools, such as piston rings and ball-bearing races, is described.
Abstract: Examples of the use of a casehardening (CH) method (surface passivation and standard heat treatment) developed to increase hardness and corrosion resistance and to lower the surface roughness of various components and tools — glass molds. piston rings and ball-bearing races — are presented in this paper.