


Vol 57, No 11-12 (2016)
- Year: 2016
- Articles: 20
- URL: https://journals.rcsi.science/0026-0673/issue/view/14626
90th ANNIVERSARY OF THE DEPARTMENT OF METAL SCIENCE OF THE URAL FEDERAL UNIVERSITY
Formation of Structure of Wear-Resistant Steels 150KhNML and Kh12MFL Upon Quenching
Abstract
The effect of the temperature of heating for quenching on the content of retained austenite and its resistance to the deformation-induced martensitic transformation, the hardening capacity, and the resistance to abrasive wear are studied for high-carbon tool steels 150KhNML and Kh12MFL of pearlitic and ledeburitic classes.



Article
Changes in the Structure and Properties Under Deformation of Austenitic-Ferritic Steel at Room and Negative Temperatures
Abstract
The effect of compressive, tensile, and impact deformation on the mechanical and physical properties of a complexly alloyed austenitic-ferritic steel for making springs and elastic members is studied at room and negative temperatures. The structural changes and their interrelation with the mechanical properties are analyzed.



Special Features of Friction Treatment of Steels of the Spring Class
Abstract
The influence of surface friction deformation on the structure and properties of malleated ribbons from spring steels of martensitic and austenitic types is studied. X-ray diffraction and electron microscopic analyses are performed. A “sliding preform – immobile indenter” loading scheme providing friction deformation of long-length ribbon preforms is discussed.



Twip-Effect in Nickel-Free High-Nitrogen Austenitic Cr – Mn Steels
Abstract
The mechanism of plastic straining and the structure of high-nitrogen austenitic steel 06Kh18AG19M2 (0.81% N) after a hardening treatment involving quenching, aging, and plastic deformation by equichannel angular pressing (ECAP) are studied. Electron microscope investigation is used to determine the mechanism of straining and fragmentation of the structure of the steel under the ECAP, i.e., twinning. The method of x-ray diffraction analysis is used to evaluate the contribution of the parameters of structural flaws into the broadening of austenite lines under the ECAP.



Raising the Structural Strength of Systematically Alloyed Fe – Cr – Ni – Mo-Base Maraging Steels
Abstract
The effect of systematical Mo, Ti, Al and Ca alloying of corrosion-resistant maraging steels of type Kh11N10M2T and of the modes of their heat treatment on the phase composition, combination of properties and resistance to brittle fracture is studied. It is shown that the structural strength of the steels can be raised by additional alloying with copper and formation of a regulated content of metastable retained austenite.



Effects of Aging on the Evolution of Microstructure and Mechanical Properties of an Al – Li – Cu – Mg Alloy with Ag, Zr, Mn, and Zn Additives
Abstract
The microstructure and the post-aging hardness of an Al – Li – Cu – Mg alloy is studied by the methods of transmission electron microscopy. Tensile tests are performed. The volume fraction and the size of the particles of the δ′, S and T1 phases are shown to be dependent on the aging temperature and time. The effect of the precipitates of the δ′, S and T1 phases on the hardening of the Al – Li – Cu – Mg alloy during aging is determined.



Evolution of the Structure of Local Regions of Fused Metal in Explosion-Welded Nickel-Aluminum Composites Under Heat Treatment
Abstract
The methods of electron, optical, and atomic force microscopy are used to study the structure, morphology and phase composition of local regions of fused metal in an explosion-welded nickel-aluminum composite. It is shown that the diffusion zone formed due to the heat treatment repeats the contour of the fuse in the first stage and then “absorbs” it upon duration of the hold thus leveling the phase composition. ANi2Al3 Aluminide layer forms on the side of nickel and a NiAl3 layer forms on the side of aluminum.



Optimization of Heat Treatment Modes of Steel 4Kh5MFS for Metal Conduits of Hot-Chamber Pressure Casting Machines According to Results of Endurance Tests in Molten TsAM-4-1
Abstract
Amethod and a scheme of a device for testing the fatigue endurance and dissolution of die steels in cast melts are presented. The laws of dissolution and the endurance of steel 4Kh5MFS in molten TsAM-4-1 are considered as a function of the mode of the heat treatment, the temperature of the melt, and the torsional deformations. The results of the metallographic studies are used to determine the dominant kinds of fracture of steel 4Kh5MFS in the process of fatigue testing in molten TsAM-4-1 upon variation of the amplitude of the torsional deformation and of the temperature of the melt.



A Study of the Effect of Two-Stage Tempering on Mechanical Properties of Steel 30CrMnSi Using Analysis on Response Surface in Design of Experiment
Abstract
The mechanical properties of steel 30CrMnSi (30KhGSA) are studied upon optimization of the mode of heat treatment with respect to four parameters [the duration of austenitization (15 – 40 min), the temperature of the first tempering (480 – 530°C), the temperature of the second tempering (the temperature of the first tempering ± 50°C), the duration of the second tempering (60 – 100 min)] and upon changing the cooling medium in quenching, first tempering, second tempering, and second refinement. The parameters are optimized using the method of analysis on the response surface for 30 tests. The structure of the steel after the treatment by the optimized modes is studied by scanning electron microscopy, including the methods of back-scattered electrons and energy dispersive analysis.



Elimination of Coarse-Grain Property in Steel 25KhN3MFA After Overheating to Different Temperatures
Abstract
The effect of the temperature of overheating in the range of 950 – 1250°C on the texture and grain size of steel 25KhN3MFA subjected to subsequent heating at 700 – 1100°C at a rate of 100 K/h is studied. The effect of the initial texture and grain size on the temperature of disappearance of large grains is determined. Recommendations are given on application of the results obtained for choosing heat treatment regimes for large forgings.



Raising the Fatigue Resistance of Titanium Alloys by High-Speed Deformation in the Range of Polymorphic Transformations
Abstract
Methods for raising the fatigue limit of critical parts by forming the required properties and structure in preforms from α + β titanium alloys by high-speed pressing at a temperature above the point of polymorphic transformations and subsequent heat treatment are described. Amethod for experimental determination of expedient thermomechanical regimes for raising the fatigue limit of the materials of articles is considered for billets from alloy VT9.



Structure and Mechanical Properties of Shape-Memory Alloys of the Ti – Ni – Cu System
Abstract
The effect of copper additives in an amount of up to 35 at.% on the structure and phase transformations in ternary Ti – Ni – Cu alloys in conventional microcrystalline, submicrocrystalline and nanocrystalline states is studied. Complete diagrams of thermoelastic martensitic transformations B2↔B19′, B2↔B19↔B19′ and B2 ↔ B19 are plotted as a function of the copper content. Special features of variation of the microstructure are determined. Tensile mechanical properties including the parameters of the shape memory effect are measured.



Structural and Phase State of Fractured Rotor of High-Pressure Steam Turbine
Abstract
The structural and phase state of the metal of a fractured rotor of a steam turbine is studied with the use of modern methods of physical research. The metal is shown to contain gradient structures. The cause of the failure of the rotor is established. The gradient structures are determined by the developed method of acoustic scanning.



Aluminum Alloys
Low-Distortion Quenching of Aluminum Alloys in Polymer Media
Abstract
The cooling capacity of the Aqua-Quench 260 quenching medium with different concentrations of polyalkylene glycol (12, 15, 22 and 30%) is studied. Cooling curves and dependences of the cooling rate on the temperature of the polymer medium are plotted. The mechanical and corrosion properties of pilot pressings from the most widely used aluminum forging alloys V95pch, AK4-1ch, AK6ch and 1933 quenched in a solution of Aqua-Quench 260 with an additive of polyalkylene glycol are determined in comparison with quenching in hot and cold water.



Heat Treatment
Effect of Volume-Surface Hardening on the Cyclic Strength of Fragments of Solebars of Freight Bogies
Abstract
The effect of volume-surface hardening (VSH) on the mechanical properties obtained in static and dynamic cyclic endurance tests of fragments of solebars from steel 20GL is studied. The VSH is shown the raise the mechanical properties of the fragments, i.e., the ultimate strength increases by a factor of 1.6 – 2, the conventional yield strength increases by a factor of 1.3 – 1.6, the bearing capacity increases by a factor of 2.6, the endurance limit increases by 10%, and the cyclic strength (durability) in the presence of a stress concentrator in the form of a notch increases by a factor of 3 at preserved high ductility.



Structural Steels and Alloys
Hardening of Austenitic Nitrogen High-Manganese Aluminum Alloys Under Heat and Thermomechanical Treatment
Abstract
The effect of the contents of aluminum, carbon and nitrogen on the production of thermally and mechanically stable austenitic alloys based on the Fe – (20 – 25)% Mn – (5 – 10)% Al – (0 – 10)% Ni – C – N system and the efficiency of the hardening of such alloys by nitrogen additives are studied computationally and experimentally. The experimental results confirm the adequacy of the computation of the phase composition and of the estimation of the solid-solution and precipitation hardening of these alloys.



Titanium Alloys
Effect of Microalloying, with Rem Inclusively, on the Structure, Phase Composition and Properties of (α + β)-Titanium Alloy
Abstract
The effect of microalloying with yttrium and zirconium in the amount of 0.06 and 0.07 wt.% respectively on the formation of structure, phase composition and measured hardness characteristics of a two-phase titanium alloy of the Ti – Al – Mo – V – Cr – Fe system is studied. The laws of variation of the phase composition and structure of the alloy with microadditives in the temperature range of 700 – 950°C and during subsequent cooling in water and air are determined. The diagram of variation of the phase composition of the alloy under water quenching is plotted.



Refractory and Shape-Memory Alloys
Special Features of Creep and Long-Term Strength of Single-Crystal Refractory Nickel-Base Alloys
Abstract
Results of experimental studies of creep in a wide range of temperatures and stresses are presented for three modern single-crystal nickel-base alloys. A method for determining the creep characteristics by tests including step increase of the tension is suggested and tested. The effect of transition into plastic condition on the creep parameters, the influence of the chemical composition and loading conditions on the duration of creep stages I, II and III, and the conditions of appearance of crystallographic and not crystallographic modes of fracture are analyzed. Possible simple approximations of the creep curves are considered with allowance for the accumulation of damage and occurrence of unsteady creep stages.



Fracture
Formation of Zones of Plastic Strain in Quenched and Tempered Steel 09G2S During Dynamic Tests
Abstract
The shape and size parameters of zones of plastic strain under fracture surfaces of quenched and tempered steel 09G2S are estimated. The shapes of the zones of plastic strain (PSZ) are studied after all the tested modes of heat treatment. Maps of distribution of the microhardness are plotted for complete PSZ of specimens standardized by GOST 9454–78 with relative crack length 0.55 and for specially prepared specimens with additional side V-notches with relative crack length 0.5.



Welded Joints
Welding of Low-Alloy Steels with Fiber Laser in the Mode of Beam Scanning
Abstract
Metallographic studies and mechanical tests of welded joints formed by a fiber laser in the mode beam scanning in two passes are performed. The laws of formation of the joint, the process of laser beam welding in the mode of scanning, and the effect of the thermal action of the second welding pass on the metal of the weld are described. The process of laser welding with beam scanning is shown to have advantages.


