Water-Acetonitrile Ratio in Perchlorate Cadmium Bath and the Effectiveness of the Addition of Crown-Ester

It is shown that the strongest deceleration of the electrodeposition of cadmium in inhibited media is observed in the domain of loosening the structure of a mixed solvent (0.45 x ₂ 0.25) when the molecular adsorption of organic solvent on Cd is maximum. The process is maximally facilitated in the domain of ordering the acetonitrile's (AN) structure (0.9 x ₂ 0.75), where perchlorate anions dominate at the cathode surface. Crown-ester exhibits maximum inhibition effect under the conditions of preferential adsorption of its molecules, i.e., in the domain of the prevalence of the nonaqueous component in the mixture (x ₂ 0.95).     

Change in structure of an iron-chromium alloy during service

Conclusions As the result of long high-temperature heating the structure of the iron-chromium alloy changes. After service at 1280–1300°C for 500 h light precipitates at the boundaries and in the body of the grain enriched with chromium and molybdenum are observed, which may be considered as the result of separation of the ferrite and as a preparatory stage before precipitation of -phase. In the surface zones of the feeder, nitride and oxide inclusions and products of gas corrosion are observed.Institute of Problems of Casting, Academy of Sciences of the Ukrainian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 29–30,January, 1985.     

Converting jarosite residues into compact hematite products

Sodium jarosite is readily converted into hematite by hydrothermal reaction at temperatures greater than 220°C. Although the initial acid and ferric ion concentrations must be kept low to avoid the unwanted formation of Fe(SO₄)(OH), the conversion reaction is unaffected by modest concentrations of ZnSO₄, FeSO₄ or Na₂SO₄. Hematite seeding is desirable to promote the reaction and to stabilize the reaction system. The hematite conversion product will likely contain ～0.5% Zn and ～2% SO₄; most of the arsenic in the jarosite will remain with the hematite.     

Effect of deposition conditions on the properties and annealing behavior of cold-sprayed copper

The deposition of copper by cold gas dynamic spraying has attracted much interest in recent years due to the capability to deposit low-porosity oxide-free coatings. However, it is generally found that as-deposited copper has a signicantly greater hardness, and potentially lower ductility, than bulk material. In this article, copper was deposited by cold spraying using helium as the driving gas at both 298 and 523 K. Evidence is presented indicating that the material sprayed at the lower temperature exhibits a lower dislocation density throughout the grain structure than the material sprayed at the higher temperature. The low stacking fault energy of copper restricts recovery during annealing, and thus microstructural changes during annealing only proceed once recrystallization begins. The material sprayed at low temperature (with the low dislocation density) exhibited recrystallization at annealing temperatures as low as 373 K with a corresponding reduction in hardness. However, the copper sprayed with helium at 523 K was resistant to annealing at temperatures up to 473 K where the dislocations in the structure prevented recrystallization. However, at higher temperatures, recrystallization did proceed (with corresponding reductions in hardness). The fracture behavior of the copper that was cold sprayed with helium at 523 K, both in the as-sprayed condition and following annealing, was measured and explained in terms of the annealing mechanisms proposed. The original version of this paper was published in the CD ROM Thermal Spray Connects: Explore Its Surfacing Potential, International Thermal Spray Conference, sponsored by DVS, ASM International, and HW International Institute of Welding, Basel, Switzerland, May 2–4, 2005, DVS-Verlag GmbH, Düsseldorf, Germany.     

Phase diagram and electrical behavior of silicon-rich iridium silicide compounds

The iridium-silicon phase diagram on the silicon-rich side was investigated by means of X-ray powder diffraction, density, differential thermal analysis (DTA), metallography, microprobe analysis, and electrical resistivity. Attempts were made to prepare eight previously reported silicon-rich iridium silicide compounds by arc melting and Bridgman-like growth. However, microprobe analysis identified only five distinct compositions: IrSi, Ir₄Si₅, Ir₃Si₄, Ir₃Si₅ and IrSi_≈3. The existence of Ir₂Si₃, Ir₄Si₇, and IrSi₂ could not be confirmed in this study. DTA in conjunction with X-ray powder diffraction confirm polymorphism in IrSi_≈3, determined to have orthorhombic and monoclinic unit cells in the high and low temperature forms. A eutectic composition alloy of 80.5 ± 1 at.% Si was observed between IrSi_≈3 and silicon. Both Ir₄Si₅ and Ir₃Si₄ exhibit distinct metallic behavior while Ir₃Si₅ is semiconducting. IrSi and IrSi_≈3 exhibit nearly temperature-independent electrical resistivities on the order of (5–10) × 10⁻⁶ ω m.     

A Heat Treatment to Produce a Coarse-α-Particle Size in Ti–6Al–4V

Metallurgical and Materials Transactions A - A heat-treatment method to develop a coarse-α-particle size in Ti–6Al–4V with a fully-globular (equiaxed) microstructure was developed....     

Effects of an Ingot Smelting Method and Pressure Treatment Modes on the Structure of Deformed TiNi-Based Alloy Semi-Finished Products

Metallurgist - It is shown that the pressure treatment of titanium nickelide alloys should be carried out in two stages. At the first stage, ingots are deformed in order to transform the brittle...     

Metallurgical Features of Plasma Surfacing Repair of Magnesium Alloys

Metallurgist - Results are provided for studying formation of the structure and properties of products made of high-strength light alloy ML5 of the magnesium-aluminum-manganese-zinc system using...     

Sulfur in chromia

The solubility of sulfur in chromia has been studied in H₂-H₂O-H₂S tagged with³⁵S at 973 and 1173 K at low oxygen and sulfur partial pressures typical for coal gasification-systems. For monocrystalline samples, it has been shown that sulfur-containing species are only present adsorbed on the surface of the specimens and can be removed by ultrasonic cleaning in acetone. The surface coverage after 4 weeks of exposure to H₂-H₂O-H₂S was between 2.8 and 19.3% of a monolayer. In polycrystalline chromia, sulfur was located only in pores and cracks of the sample. In dense, compact areas of the specimens the solubility of sulfur was below the detection limit of autoradiography, which was estimated to be better than 0.17 ppm.