Metastable manganese austenite as a structural base of high-stability steels conditions of dynamic contact loading

Important regular features of the structure and special features of the behavior of metastable manganese austenite under conditions of quasistatic deformation and dynamic contact loading are considered. Based on the correlation of the energy of packing defects of manganese austenite with the kinetics of deformation martensitic transformations { , } and the capacity for deformation strengthening and relaxation of stresses, principles for choosing the base composition of metastable austenitic steels with a high operating stability for different conditions of dynamic contact loading are established.     

On the Removal of Aluminide Coating from Blades of Gas Turbin Engine

The peculiarities of removing -11 coating from 32 type alloy in an acidic etching bath depending on the concentration and ratio between the amounts of potassium bichromate and ammonium heptamolybdate additives are studied with gravimetrical and electrochemical methods. The results are explained by the peculiarities of bichromate and molybdate ions adsorption at the surface and their oxidizing properties. Baths providing sufficiently quick removal of the coating at a minimum alloy surface etching are recommended.     

Constitution and Crystallography of Thin Thermal-Oxide Layers on varepsilon -Fe2N1-x: A HREM Investigation

Oxide layers formed on varepsilon -Fe₂N_1-x wereinvestigated with X-ray photoelectron spectroscopy, X-ray diffraction, andin particular with high-resolution transmission electron microscopy. Priorto oxidation, the varepsilon -Fe₂N_1-x substrates wereeither exposed to air at room temperature, or subjected to asputter-cleaning pretreatment, or to a sputter cleaning with an additionalannealing pretreatment. The samples were oxidized at 400 or 573 K in pureO₂ at 8.0x10^-2 Pa or at 10⁵Pa. All oxide films contained magnetite ( -Fe₂N_1-x)as a major constituent. On samples that were sputter-cleaned and annealedprior to oxidation as well as on the air-exposed sample, wüstite,(Fe₁-O) was observed between the Fe₃O₄and -Fe₂N_1-x. On the basis of HREM, thiswüstite phase, which on -Fe does not develop at temperaturesbelow 843 K, was concluded to have a preferred crystallographic orientationwith respect to the supporting -Fe₂N_1-x grains. Nospecific orientation relation was found between Fe₃O₄ and -Fe₂N_1-x. The implications of the developmentof Fe_1-O for the evolution of the oxide film arediscussed.     

The Influence of Ozone on the Electrochemical and Corrosion Behavior of Metals in Acid Media

The corrosion–electrochemical behavior of 092, 0817, 1017132 steels, 0628 alloy, and such metals as aluminum, chromium, and nickel are investigated in ozonized acid media. The effect of ozone on the corrosion–electrochemical properties of these metals are shown to be ambiguous.     

Resistance of 1201 aluminum alloy to plastic deformation at various strain rates

Conclusion With an increase in the rate of plastic strain there is a change in the resistance of 1201 alloy to plastic deformation, which is revealed in a nontraditional decrease in _0.2 and increase in , and A_p. The characteristics _k and _t increase nonlinearally.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 56–61, August, 1989.     

Effect of the tempering temperature and time on the structure and phase composition of the AMg6 alloy

Conclusions It was determined that the decomposition of the solid solution in the AMg6 alloy begins at the grain boundaries. After a certain time interval the plate-like -phase precipitates within the grains. After a longer tempering time the platelets coagulate and take on a rounded form.At temperatures of 200 and 250°C the metastable -phase is not completely converted into the -phase, and even after a very long tempering time there is still a considerable amount of the -phase in the structure.At a temperature of 150°C or lower, only the metastable -phase occurs in the alloy even after tempering as long as 9 months.Translated from Metallovedenie i Termichesakaya Obrabotka Metallov, No. 9, pp. 59–61, September, 1966.     

General laws governing variation in properties of cast alloys of the Al-Zn-Mg system

Among existing high-strength corrosion-resistant aluminum alloys, those of the Al-Mn-Zn system are most promising. They have a different phase composition, depending on the content of magnesium and Zinc: + (Al₃Mg₂), + + T(Al₂Mg₃Zn₃), + T, + T + (MgZn2) and + The majority of industrial Al-Mg-Zn alloys correspond to the phase regions + T and + T + with respect to composition. A high level of strength and satisfactory overall corrosion resistance are characteristic for these alloys. Al-Mg-Zn alloys may, however, tend to the most dangerous form of corrosion - stress-induced corrosion cracking. Using methods of experiment planning in the study, we investigated Al-Zn-Mg alloys of various compositions for the purpose of selecting alloy compositions with a high level of mechanical properties and stress-induced corrosion cracking.All-Union Scientific-Research Institute of Aviation Materials. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 24–28, December, 1994.     

Effect of rapid cyclic electrothermal treatment on the structure of nickel steel

Conclusions The high dislocation density of austenite undergoing the transformation is due to the influence of fresh dislocations that occur during the transformation in virtue of its martensitic character and to dislocations inherited from the original phases.Since the increase of the dislocation density in austenite causes an increase in the number of martensite crystals, it can be assumed that the increase in the number of phase nuclei is due to an increase in the density of fresh dislocations. In this case the refining of martensite is due to an increase in the number of nuclei and to the barrier effect of elements of the substructure. The formation of atmospheres of impurity atoms at dislocations in alloys with carbon stabilizes the austenite and intensifies recrystallization processes. Cementite particles in phase are not inherited by austenite with heating to the transformation temperature.Institute of Metal Physics, Academy of Sciences Ukrainian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 20–23, January, 1975.     

Spark-Anodic Oxide Coatings Formed on Al and Ti Alloys in Tungstate-Containing Phosphate–Vanadate Baths

Oxide coatings superficially, enriched with P, V, or W, were formed on aluminum and titanium alloys by their spark-anodizing in aqueous baths containing NaH₂PO₄ · 2₂ (45.9 g/l), NaVO₃ · 2₂ (15 g/l), and different concentrations of Na₂WO₄ · 2₂. The coatings' composition was investigated with laser mass spectrometry and microprobe analysis, while the state of phosphate groups in solution, was with NMR spectroscopy using ³¹P nuclei. The elemental composition of the coatings presumably depends on the composition and concentration of vanadate-tungstate-phosphates and vanadate-tungstates in solution.     

Control of the structure of two-phase titanium alloys in thermomechanical working

Conclusions The embryos of - and -phases obtained in +-titanium alloys in hardening and aging are preserved in cold working and become centers of growth of these phases in subsequent aging. As a result it is possible to obtain -phase or more uniformly distributed -phase in cold-worked and aged alloys.Moscow Institute of Electronic Machine Building. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 53–55, May, 1984.     

Thermal Resistance of Low-Alloyed Chromium Alloys

The oxidation kinetics of low-alloyed -2 and 1-17 chromium alloys is investigated at a temperature from 1273 to 1673 K for 1000 h. It is shown that even at a temperature from 1473 to 1673 K the heat resistance of these alloys is higher than that of the 648 nickel-containing alloy at a temperature from 1273 to 1373 K. This allows to recommend the alloys as heat-resistant materials operating at a temperature up to 1573 K.     

Protection of Sintered Steels against Corrosion in Neutral Media with an N-M-1 Inhibitor

The effect of an N-M-1 inhibitor (a salt of cyclohexylamine and C₁₀ to C₁₆ aliphatic acids) on the corrosion of sintered powder steels 13 and 141 (with the 14 to 17% porosity) in distilled or tap water at 20 to 80°C, as well as in 0.05 M Na₂SO₄ solution, is studied by gravimetric and electrochemical methods. The protective concentration of the inhibitor is lower in distilled, than in tap water or sodium sulfate solution. The protective action decreased with an increase in temperature. In tap water or sodium sulfate solution, the corrosion-inhibiting effect is weaker for 13 than for 141.     

Quasiequilibrium treatment of gas-solid reactions. III. Rate of volatilization of tungsten by high-temperature oxidation

Theoretical predictions computed on the basis of the quasiequilibrium treatment of gas-solid reactions are compared with existing experimental data on the rate of volatilization (erosion) of solid tungsten by reaction with gaseous O₂ at high temperature ( 1300° T 3600° K) and low pressure (4.5 × 10^–7 11.5 Torr). The only unknown parameter in the analysis is the equilibrium probability, , defined as the fraction of the impinging O₂ molecules that attain thermochemical equilibrium at the tungsten surface rather than undergoing nonreactive scattering (e.g., reflection). An approximate expression for is estimated by a straightforward empirical procedure that is consistent with the quasiequilibrium treatment. The theoretical results based on this expression for T because appears to be an exponential function ofT; (b) In the intermediate region, the formation of volatile oxides decreases sharply with increasingT because atomic oxygen becomes the thermodynamically favored reaction product, thereby causing _W to decrease with increasingT; (c) In the highest region, _W again increases withT as a result of the formation of WO and the sublimation of W.This work was supported by the Joint Services Electronics Program [Contract DA28-043-AMC-02536(E)] and by NASA [Grant NGR-22-009-091].     

Effect ofθ-alumina formation on the growth kinetics of alumina-forming superalloys

Alumina-forming ODS superalloys are excellent oxidation-resistant materials. Their resistance relies upon the establishment of a stable, slow-growing, and adherent -alumina. In the present investigation, these alloys exhibited unstable and relatively less adherent -alumina phase, which increased the oxidation rate in the transient stage and converted into -alumina in the later part of the exposure. The oxide-growth process was found to depend upon various parameters such as temperature, time, and presence of an active elecment in the superalloy. Characterization carried out by XRD, SEM/EDAX, and AES on oxidized ODS and non-ODS alloys demonstrated a significant influence of the active element, Y, on the transformation of - to -alumina. SIMS analysis of two-stage oxidation at 900°C for two different durations evidently showed that the change in the transport process is due to -to--alumina transformation. On the basis of these results, a new and consistent mechanism is proposed to explain the influence of -alumina and its transformation on growth kinetics and the effect of yttrium on the transformation leading to good scale adherence and oxidation resistance.     

Delta-ferrite in hot-deformed metal of corrosion-resistant maraging steels

In some cases the -ferrite inherited from ingots is present in the hot-deformed metal of corrosion-resistant maraging steels. The residual -ferrite exerts a negative effect on the technological and operating characteristics of the metal. The present work presents results on transformations of -ferrite and variations of the properties of steels in quenching by different regimes. Recommendation on heat treatment of steels containing -ferrite are presented.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 36 – 39, July, 1995.     

Effect of nitrogen and chromium on the mechanical properties of austenitic steels at −196°C

Conclusion Nitrogen lowers and chromium raises (with >3% N) the strength (_b0.2), ductility (, ), and fracture toughness of austenitic stainless steel of the Kh(18-24)N20 type in the aged condition. The effect of chromium on the properties is due to a change in the solubility of nitrides.I. P. Bardin Central Scientific-Research Institute of Ferrous Metallurgy. Translated from Metallovedenie Termicheskaya Obrabotka Metallov, No. 8, pp. 6–8, August, 1979.     

Role of Adsorbed Metal Complexes in Cadmium Electrodeposition from Iodide-Containing Aqueous Ethanol

Structurization phenomena in a mixed solvent were found to determine, by affecting the solvation degree of an anion, its adsorptivity at the electrode and, consequently, the surface concentration of the nonaqueous solvent. The formation of activated Cd²⁺ complexes with iodide anions in an adsorbed layer is usually accompanied by accelerating the electrode reaction. The desalting effect of the mixed solvent in the zones of its structural stabilization is mainly manifested as the enhanced adsorptivity of iodide anions and the correspondingly facilitated discharge of metal ions. The highest discharge rate was found at ₂ 0.9 when the structure of EtOH is ordered with monomeric water molecules. The highest surface concentration of EtOH and the lowest rate of cadmium electroreduction correspond to a structurally disordered mixture ( ₂ 0.4).     

Fracture mechanism of titanium at different temperatures

Conclusions Deformation of titanium at negative temperatures occurs by twinning. With increasing temperatures fracture occurs with viscous flow of titanium. The transformation is accompanied by a change from viscous flow to slip in different planes.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 47–48, July, 1976.     

Oxidation ofγ′-Ni3Al andγ′-Ni3Al(Si) intermetallic compounds at low-oxygen pressures

The oxidation behavior of -Ni₃Al and -Ni₃Al(Si) (Ni₇₅Al₂₀Si₅) intermetallic compounds was studied at 1073 K and oxygen partial pressures of 59×10^–6 atm, 1.2×10^–14 atm, and 1.2×10^–19 atm by means of a manometric apparatus, and Rhines packs of NiO/Ni and FeO/Fe, respectively. Oxidation kinetics were determined either by recording weight gains or by measuring the internal-oxidation-zone depths. The structures and morphologies of oxides were also studied. Relatively low oxidation rates occurred for both compounds when oxidized in the manometric apparatus, while fast internal oxidation was observed for both compounds in the NiO/Ni pack. The fastest oxidation occurred in the -Ni₃Al compound in the FeO/Fe pack. A healing Al₂O₃ layer was formed on the surface of -Ni₃Al(Si) compound in the FeO/Fe pack, indicating a synergistic effect between the solute elements in the compound at the oxygen pressures corresponding to the dissociation of FeO. The oxidation rate was found to depend on the volume expansion associated with solute-atom oxidation.     

High-resolution SIMS and analytical TEM evaluation of alumina scales onβ-NiAl containing Zr or Y

High-resolution SIMS and TEM have been used to evaluate growth processes and interfacial segregation occurring in -Al₂O₃ scales grown at 1200°C on -NiAl containing zirconium or yttrium.¹⁸O/SIMS shows that the extent of aluminum diffusion occurring during -Al₂O₃ growth is reduced by the presence of these alloying elements, which are seen by SIMS imaging as oxide particles within the scale. STEM/EDS of the same oxide scales show that zirconium and yttrium also segregated to the oxide-alloy interface to the extent, respectively, of 0.15 and 0.07 of a monolayer and to oxide grain boundaries (0.2 monolayer). The complementary information provided by SIMS, TEM, and STEM provides a better understanding of the role of reactive elements in modifying scale-growth processes.