


卷 59, 编号 3-4 (2017)
- 年: 2017
- 文章: 24
- URL: https://journals.rcsi.science/0026-0673/issue/view/14644
Aluminum Alloys
A Study of the Effect of Temperature and Rate of Cooling Under Crystallization on the Structure of Cast Alloy Al – 30 at .% Cu
摘要
The methods of metallographic, differential thermal and x-ray phase analysis, light and electron microscopy, and measurement of microhardness are used to study the morphological features of the structure of hypereutectic alloy Al – 30 at.% Cu formed due to cooling of liquid phase at a rate of about 2 and about 104 K/sec after superheating above the liquidus. A comparative study of structural and phase transformations in castings is performed.



Kinetics of Accumulation of Damage in Surface Layers of Lithium-Containing Aluminum Alloys in Fatigue Tests with Rigid Loading Cycle and Corrosive Effect of Environment
摘要
High-resolution methods of metal physics research including electron, laser and optical microscopy are used to study the kinetics of the accumulation of slip lines and bands and the corrosion damage in the plastic zone of specimens of aluminum-lithium alloys 1441 and B-1469 in rigid-cycle fatigue tests under the joint action of applied stresses and corrosive environment. The strain parameters (the density of slip bands, the sizes of plastic zones near fracture, the surface roughness in singled-out zones) and the damage parameters (the sizes of pits and the pitting area) are evaluated.



Article
Microstructure and Mechanical Properties of Welded Joints of Aluminum Alloy AA7020-T6 Obtained by Friction Stir Welding
摘要
Plates from alloy AA7020 (Al – Zn – Mg) with a thickness of 4.5 mm are studied after T6 heat treatment and friction stir welding. Tensile and bending tests are performed. The hardness of the welds is measured in transverse direction. The microstructure over cross section of a weld is studied by the methods of light and transmission electron microscopy. The weldability of alloy AA7020 by friction stir welding is shown to be high.



Effect of Quenching Medium on Mechanical Properties of Alloy Al7049-T6 and Lowering of its After-Machining Warpage
摘要
Aluminum alloy Al 7049 is studied in state T6. Heat treatment of the specimens is performed in different quenching media (cold water, boiling water, aqueous polymer solutions). The mechanical properties and the Brinell hardness of the alloy are determined after different modes of heat treatment. Comparative analysis is used to find the maximum residual stresses responsible for warpage of the alloy after machining. The relation between the warpage and the dimensionless Biot number is obtained. Quenching modes removing the warpage in billets of Al7049 are determined.



Secondary Heating Under Quenching Cooling of Aluminum Alloys
摘要
Variants of secondary heating of aluminum alloys are considered, i.e., under quenching of plates in a water tank or on a horizontal quenching unit with water jet cooling, under continuous quenching of strips, and under quenching of tubes in vertical furnaces. Recommendation are given for removal or substantial reduction of the intensity of secondary heating under industrial conditions.



Effect of Zn and Mn Additions on the Wear Resistance of Cast Alloy Mg – 5% Al – 1% Si
摘要
The effect of additions of Zn and Mn (from 0.5 to 4%) on the microstructure of alloy Mg – 5% Al – 1% Si is studied by the methods of x-ray diffractometry and light and scanning electron microscopy. The strength parameters are determined in tensile and wear tests. It is shown that particles of Mg2Si precipitate in the matrix and particles of Mg17Al12 precipitate on grain boundaries upon the introduction of low contents of Zn and Mn. Phases MgZn and Al6Mn precipitate at a high content of the additions. An optimum concentration of Zn and Mn is chosen for raising the wear resistance of alloy Mg – 5% Al – 1% Si.



Electromechanical Surface Hardening of Tubing Steels
摘要
Results of metallographic studies of the structure of steels 38G2S and 37G2F and steels of group D after electromechanical surface hardening of tube specimens over the external diameter are presented.



Effect of Production Process on Microstructure and Mechanical Properties of Copper Coatings of Jet Charges
摘要
Special features of formation of the grain structure and mechanical properties of copper during recrystallization annealing after cold deformation with a wide range of reduction are studied. The constants of the Hall-Petch equation are determined for copper, the microstructure of which forms in the course of plastic deformation and subsequent heat treatment. The results of the study are allowed for in the process of production of claddings for jet charges.



Kinetic Aspects of Formation of Carbonitride Layer
摘要
The laws of formation and growth of carbonitride layer in steels 40G2, 38KhMA, 40KhN2MA, and 09GSF at a temperature of 560°C are studied. Metallographic methods are used to determine its composition, location and length. Equations for computing the lengths of the carbonitride phase and of the layer due to surface cyaniding are derived.



Effect of Carbonitriding on Corrosion Resistance of Steel 30MnB5 in Two Acidic Environments
摘要
Corrosion resistance of steel 30MnB5 is studied after carbonitriding, after conventional quenching, and without treatment. Corrosion tests are performed for from 24 to 168 h in two acidic environments (in a hydrochloric acid solution with 10% mole fraction and in fertilizer-containing soil). It is shown that the rate of corrosion of the steel in both environments after carbonitriding is lower than after quenching).



Formation of Cast Structure in High-Manganese Steels Under Different Rates of Cooling of Castings
摘要
The effect of the rate of cooling on the structure and properties of castings from a high-manganese steel is studied. The level and the sign of the residual stresses, the size of the austenite grains and the microhardness of the austenite, the content and morphology of the carbide phase, and the hardness of the cast steel are determined. The optimum cooling conditions producing the most homogeneous structure in a casting are obtained. Comparative analysis of the effect of the cooling rate and of the microhardness of the austenite on the morphology and size of the carbide phase is performed.



Novel High-Alloy Boron-Containing Steels for Driven Elements of Tilling Machines
摘要
Novel boron-containing steels for driven elements of tilling machines with mechanical properties and wear resistance not inferior to the foreign counterparts are developed.



Structure and Corrosion Resistance of Welded Joints of Alloy 1151 in Marine Atmosphere
摘要
The corrosion behavior of joints formed by TIG and IMIG welding from clad sheets of heat-hardenable aluminum alloy 1151 of the Al – Cu – Mg system is studied. The corrosion tests are performed in an aqueous solution of NaCl in a salt-spray chamber. The welded joints are subjected to a metallographic analysis.



Microstructure and Salt Fog Corrosion Behavior of AA2219 Friction-Stir-Welded Aluminum Alloy
摘要
Plates (8.1-mm-thick) from aluminum alloy AA2219-T87 are studied after friction stir welding. The plates are subjected to salt fog corrosion tests according to ASTM B117 at different pH values and different spraying times. The regions affected by corrosion are studied in different zones of welded joints by the methods of optical and transmission electron microscopy. The corrosion resistance is determined in acid, basic and neutral solutions. The resistances of the base metal and of the zones of welded joints are compared.



Effect of Carbonitriding on the Susceptibility of Medium-Carbon Alloy Steels to Temper Brittleness
摘要
The effect of carbonitriding as a finishing operation of hardening of the thread of drill pipes on the properties of the matrix metal, its temper brittleness in particular, is studied. The cold brittleness is evaluated with the help of tests for impact toughness. Steels for the production of drill pipe locks for operation at negative temperatures are recommended.



Structure and Properties of “Magnesium Alloy – Carbon Nanotubes” Nanocomposite and their Optimization Using Design of Experiments
摘要
A nanocomposite obtained by introduction of carbon nanotubes into the surface layer of magnesium alloy AZ31B by the method of friction stir processing is studied. Dependences of the hardness and wear resistance on the speed of motion of the friction tool, the speed of rotation of the friction head, the number of passes of the tool and the relative content of carbon nanotubes in the layer are determined. The method of design of experiment is used to find the optimum modes for production of a nanocomposite with high hardness and wear resistance.



Magnesium Alloys
Effect of Iron Impurity on the Phase Composition, Structure and Properties of Magnesium Alloys Containing Manganese and Aluminum
摘要
Results of a study of the interaction between iron impurity and manganese and aluminum alloying elements during formation of phase composition in alloys of the Mg – Mn, Mg – Al, Mg – Al – Mn, and Mg – Al – Zn – Mn systems are presented. It is proved that this interaction results in introduction of Fe into the intermetallic phase. The phase compositions of model magnesium alloys and commercial alloys MA2-1 and MA5 are studied. It is shown that both manganese and aluminum may bind the iron impurity into phases. Composite Fe-containing intermetallic phases of different compositions influence differently the corrosion resistance of magnesium alloys.



Deformation and Heat Treatment
Effect of Parameters of Deformation and Thermal Deformation Aging on the Impact Toughness of Structural Steel After TMT and HT
摘要
Rolled sheets with a thickness of 60 mm are studied after thermomechanical rolling and after an additional heat treatment. The conditions of the deformation and thermal deformation aging are shown to affect the impact toughness of the low-carbon microalloyed steel. The changes in the critical temperatures of the impact toughness due to increase in the degree of preliminary cold deformation and under additional heating of the steel to 250°C are determined. The parameter of the susceptibility of surface and central (over the thickness) layers of a thick sheet to mechanical aging is computed.



Thermochemical Treatment
Control of the Structure of Diffusion Layer in Carbon Steels Under Nitriding with Preliminary Deposition of Copper Oxide Catalytic Films
摘要
The effect of thin films of copper oxide deposited before nitriding on the phase composition and the kinetics of growth of diffusion layers in carbon steels is considered. The process of formation of an oxide film involves chemical reduction of pure copper on the surface of steel specimens from a salt solution and subsequent oxidation under air heating. The oxide film exerts a catalytic action in nitriding of low- and medium-carbon steels, which consists in accelerated growth of the diffusion layer, the nitride zone in the first turn. The kinetics of the nitriding process and the phase composition of the layer are controlled by the thickness of the copper oxide precursor, i.e., the deposited copper film.



Choice of Boundary Condition for Solving the Diffusion Problem in Simulation of the Process of Vacuum Carburizing
摘要
Comparative analysis of three kinds of boundary condition for solution of the diffusion equation in a mathematical model of vacuum carburizing (low-pressure one) is performed for plotting the carbon concentration curves in carbon and alloy steels. With allowance for the special features of mass transfer in formation of the diffusion layer and for the effect of control factors of the carburizing process, the mass transfer coefficient in the equation of the boundary condition of the third kind is evaluated with the help of parametric equations.



Structural Steels
Refinement of the Structure of Microalloyed Steels Under Plastic Deformation Near the Temperatures of Polymorphic Transformation
摘要
The effects of plastic deformation near the temperatures of the F → A phase transformation and of deformation-induced ferritic transformation (DIFT) on the structure and properties of microalloyed ferritic-pearlitic steels are studied. It is shown that the refinement of the structure of the steels due to the F → Atransformation during heating and due to the DIFT under plastic deformation and subsequent cooling raises the mechanical properties of the metal. Modes of hot rolling are suggested for structural ferritic-pearlitic steel 17G1S-U in order to form an ultrafine-grained structure with elevated mechanical properties.



Magnetic Alloys
A Study of the Causes of Failure of Permanent Magnets from Cast Hard Magnetic Alloys
摘要
The microstructure and magnetic properties of permanent magnets fabricated from cast hard magnetic alloys of the Fe – Ni – Al system with cobalt addition of type YuNDK are studied. The causes of failure of such magnets in operation are determined. Recommendations are given for correcting the melting process and the modes of heat treatment of magnets in order to provide the required properties without disturbing the integrity of the magnets.



Simulation
Simulation of Structural Transformations in Heating of Alloy Steel
摘要
Amathematical model for computer simulation of structural transformations in an alloy steel under the conditions of the thermal cycle of multipass welding is presented. The austenitic transformation under the heating and the processes of decomposition of bainite and martensite under repeated heating are considered. Amethod for determining the necessary temperature-time parameters of the model from the chemical composition of the steel is described. Published data are processed and the results used to derive regression models of the temperature ranges and parameters of transformation kinetics of alloy steels. The method developed is used in computer simulation of the process of multipass welding of pipes by the finite-element method.



Erratum
Erratum to: Evolution of Dislocation Structure in a Ni3Al Single Crystal Under the Conditions of High-Temperature Superplasticity


