Extracting and Refining Germanium

Germanium products are well suited for many advanced materials applications—lens blanks for infrared optics, dioxide for electronic and catalyst use, “intrinsic” metal for radiation detectors, and electronic grade tetrachloride for optical fibers. Before undertaking these applications, however, the germanium must first be recovered. This article reviews the germanium extraction and refining techniques of the late 1950’s and early 60’s, as practiced by American Metal Climax (now AMAX), and compares the practices with the more recent developments presented in current technical literature. Overall, there have been no major changes in the process chemistry of germanium extraction and refining in the period surveyed. Significant changes have, however, taken place in the engineering of process plants for producing semiconductor grade germanium. The use of zone refining for final purification of germanium metal to semiconductor grade is still required and will probably continue for some time. Finally, considerably more thermodynamic data is available for predicting the optimal germanium recovery conditions from smelter fumes than existed twenty years ago. As a result, less experimental work should be required to optimize recovery.     

Promising methods of surface hardening for titanium alloys and steels with rapid heating

Conclusion Surface electron-beam heat treatment of steels leads to formation of hardened layers 1–5 mm thick having a finely acicular martensitic structure with increased hardness. There is redistribution of alloying elements, acceleration of decomposition processes during heating of hardened specimens, and compressive stresses arise. Heating in a flashing schedule for steels reduces the overall area of inclusions up to a factor of 6.6, and combined with subsequent heat treatment it excludes nonuniform distribution of alloying elements.Use of electrodeposited coatings during electrochemical heat treatment sharply intensifies reaction diffusion processes. During siliciding of titanium alloys with a copper underlayer the thickness of diffusion layers reaches 975 m, and during carburizing of titanium with an iron coating it reaches 1050 m. In this way there is a sharp increase in titanium alloy wear resistance.With rapid heat treatment of alloys with electrodeposited and gas heat-treatment coatings there is rebuilding of the surface structure with formation of fine blocks 0.5–10 m in size, twins, and slip bands. The size and structure of the transitional diffusion zone depends on the presence of a metal underlayer, and treatment schedule. As a result of electron-beam surface treatment the adhesive strength is improved (up to _ad= 200–210 N/mm²) and the wear resistance of gas heat treatment coatings (by a factor of two to three). The friction coefficient for electrodeposited chromium coatings increases by a factor of 1.5–2 with an increase in loads by a factor of two to three.Physicotechnical Institute, Academy of Sciences of the Belorussian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 45–49, October, 1987.     

Improvement of grain refining efficiency for Mg–Al alloy modified by the combination of carbon and calcium

The effects of carbon and/or Ca on the grain refinement of the Mg–3Al alloy have been investigated in the present study. The grain size of the Mg–3Al alloy decreased steeply with increasing the Ca content when it was lower than 0.2%. And then, the grain size decreased slightly when the Ca content was increased to 0.5%. A remarkable grain refining efficiency could be obtained for the Mg–3Al alloy treated with only carbon. Further high grain refining efficiency could be obtained by the combination of 0.2%C and the optimal content (0.2%) of Ca. Therefore, Ca is an effective element to improve the grain refining efficiency for the Mg–Al alloys refined by carbon. The AlCO particles were observed in the samples refined whether by only 0.2%C or by the combination of 0.2%C and a little (less than 0.2%) Ca addition. These AlCO particles should be the potent nuclei for the Mg grains. However, the AlCOCa intermetallic particles were observed when Ca content was increased to 0.5%. Peculiar particles with duplex phases were found in this sample in such a state that AlCO coating film was formed on the surface of Al–Ca compounds. These particles should also be the potent nuclei for the Mg grains.     

Effect of acoustic fatigue on the concentration of vacancies in copper

Belorussian Technological Institute, Nondestructive Testing Institute, Academy of Sciences of the Belorussian SSR. Production Union "Gomsel'mash.". Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 45–46, April, 1989.     

Formation of fine-grained structure in forgings of steel 60KhN

Conclusion Forgings of steel 60KhN with a section as large as 800 mm can be heated to 1230° for final forging regardless of the subsequent forging reduction ratio. The heat treatment generally used, accompanied by the transformation, produces grain refining and mechanical properties that meet the specifications.S. M. Kirov Ural Polytechnic Institute. South Ural Machine Construction Factory. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 45–47, December, 1979.     

Nitriding of drop-forging dies

Conclusions Data from production tests indicate that two-stage nitriding of dies is the most promising process. The first stage, regardless of the composition of the steel, is conducted at 520° for 4–36 h, the holding time increasing with the alloying of the steel, since alloying elements (tungsten, chromium, molybdenum, et al.) reduce the diffusion of nitorgen in phase [5]. The second stage is conducted at 550–580°. The lower the hardness of the steel or the more highly alloyed the steel, the higher the nitriding temperature in the second stage. It is 15–30° below the tempering temperature. The holding time in the second stage depends on the case depth required. It is not always desirable to obtain the maximum hardness [2], since the highest wear resistance does not coincide with the maximum hardness.The microstructure of the case may differ, but nevertheless the dies have a long service life. Furthermore, the presence of phase in the surface layer does not impair the dies, which can be used without any additional treatment, although it is known that the formation of brittle phase leads to a sharp reduction of strength [5].It should be noted that nitriding is still a very long process, and therefore nitriding of dies is still not used in some cases, even in well-equipped plants.Physicotechnical Institute, Academy of Sciences of the Belorussian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 49–52, June, 1978.     

Corrosion and Protection of Atmospheric Rectification Towers During an Increase in the Corrosivity of Crude Oil

By the example of OAO Krasnodarekoneft', the changes that occurred in the corrosion state of an atmospheric tower of a primary oil refining section upon a changeover to more corrosive crude oil are examined. The reasons for its damage are considered. The main components of the working medium in the apparatus are analyzed in terms of their corrosivity. A complex of recommendations is developed to ensure the performance of the tower upon a changeover to more corrosive crude oil, which includes introduction of an electrodesalination and dehydration (ELAU) block, efficient choice of materials, inhibition of the primary fraction, etc.     

Recrystallization of maraging alloys

Conclusions In the maraging alloys investigated the transformation is not accompanied by refining of the original grains. The coarse-grained structure is eliminated by recrystallization of austenite at 900–1000°C, which occurs mainly by means of grain boundary migration.Physics of Metals Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 10–12, April, 1969.     

Oxidation Potentials in Matte Smelting of Copper and Nickel

The oxidation potential, given as the base-ten logarithm of the oxygen partial pressure in bars and the temperature [log pO₂/T, °C], defines the state of oxidation of pyrometallurgical extraction and refining processes. This property varies from copper making, [?6/1150]; to lead/zinc smelting, [?10/1200]; to iron smelting, [?13/1600]. The current article extends the analysis to the smelting of copper and nickel/copper sulfide concentrates to produce mattes of the type Cu(Ni)FeS(O) and iron silicate slags, FeO_xSiO₂—with oxidation potentials of [?7.5/1250].     

Reversible shape memory effect in alloys of the Mn - Cu system

The reversible shape memory effect is understood as the capacity of specimens deformed in a martensitic state to change shape (dimensions) both in heating in the process of a reverse transformation and in subsequent cooling as a result of a forward transformation. This is clearly manifested in manganese-rich Mn -Cu alloys susceptible to a diffusionless anti ferromagnetic (martensitic) transformation, as a result of which the crystal structure changes from face-centered cubic to face-centered tetragonal (f.c.c. f.c.t.).Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 9, pp. 34–37, September, 1996.     

Al—Ti—C中间合金的相组成及其细化特性

用专利方法制备出各种成分的Al-Ti-C中间合金作为铝及铝合金的晶粒细化剂。对该系列中间合金的组织和物相分析表明：在制备中间合金过程中,C与Ti反应充分,生成TiC和TiAl3两种管二相,且TiAl3析出量取决于中间合金的Ti含量和Ti/C含量比。用于纯铝的晶粒细化试验表明：与Al-Ti-C中间合金相比,Al-Ti-C中间合金的晶粒细化效率更高;Al-Ti-C中间合金只有在组织中TiC与TiAl3保持适当比例时,才能对纯铝产生良好的晶粒细化效果,不含TiAl3的Al-Ti-C中间合金的晶粒细化作用很微弱;用Al-Ti-C中间合金细化纯铝晶粒时,响应时间短,但衰退较快,且不能通过熔体搅拌法予以消除。分析和探讨了Al-Ti-C中间合金的晶粒细化机理,认为“碳化物理论” 不能充分解释Al-Ti-C的晶粒细化机理,提出“Ti在TiC或TiAl3颗粒表面富集引发包晶反应”的晶粒细化机制。     

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.     

Effect of TiC Nanoparticles Supported by Ti Powders on the Solidification Behavior and Microstructure of Pure Aluminum

A novel grain refiner consisting of TiC nanoparticles (NPs) supported by Ti powders (abbr. TiC/Ti refiner) was prepared by high-energy milling. The addition of 0.5 wt% TiC/Ti refiner converted the structure of pure Al from coarse dendrites to fine equiaxed grains with the average grain size of 114.7 μm, and it also increased the nucleation temperature of α(Al) from 656.7 to 664.4 °C. When TiC/Ti refiner was introduced into Al melt, the heat released from the Al–Ti reaction promoted the uniform dispersion of TiC NPs. The dissolution of the reaction product TiAl₃ released Ti atoms into the melt and thus formed a “Ti-rich transition region” around TiC NPs. The dispersive TiC NPs could act as the heterogeneous nuclei for α(Al) and the “Ti-rich transition region” further improved the lattice orientation relationship between Al (\(\bar{1}1\bar{1}\)) and TiC (\(11\bar{1}\)) planes, which eventually resulted in the refining of α(Al).     

Effect of lamellar structure parameters on the properties of titanium alloy VT3-1

Conclusion An increase in the ultimate breaking strength, stress-rupture strength, and fatigue limit of alloy VT3-1 with a lamellar structure may be achieved as a result of refining any parameter of the structure, particularly -phase platelet thickness, and increasing the volume fraction of secondary -phase. An increase in ductility characteristics, toughness, and creep resistance may be provided by increasing the dimensions of -colonies and primary -phase particles (up to 2.5–3.5 m) and reducing the volume fraction and dispersivity of secondary -phase lamellar precipitates. Coarsening of -grains leads to an increase in a_c, k_Q, and refinement leads to an increase in and a_n.Qualitative dependences for mechanical properties of alloy VT3-1 on lamellar structure parameters made it possible to isolate those structural parameters which have the most marked effect on properties.The properties of alloys with a finely lamellar structure (d25 m, b_{I, II}<2 m) are most sensitive to structure. In this case a change in -colony size by 10 m and -platelet thickness by 1 m affects the properties 3–20 times more strongly than a change in -grain size by 100 m. The effect of finely dispersed secondary -phase precipitates is greater, the coarser the primary -phase structure. Refinement of primary -phase structure with an increase in secondary phase platelet thickness to 1 m or more reduces the sensitivity of alloy mechanical properties to the effect of secondary -phase.With coarsening of the intragranular structure (d>25 m, b_{I, II}2 m) the effect of structural parameters d and b on properties is markedly weakened: on strength properties (_f, ₁₀₀ ⁴⁵⁰ ) by a factor of 100, on ductility (, ), by a factor of 10 to 20, and on impact strength and fracture toughness (a_n, a_c, K_Q) by a factor of five.The qualitative relationships obtained between structure and mechanical properties of alloy VT3-1 are fundamental for controlling the structure of semifinished titanium alloy products.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 52–55, July, 1986.     

Characterization of oxide structures formed on nickel-chromium alloy during low pressure oxidation at 500–600°C

Low pressure oxidation studies of Ni-18%Cr alloy were carried out at temperatures of 500–600°C for very brief periods. Detailed XPS, AES, SEM, and TEM studies identified four stages in the initial oxidation. These are: (1) formation of a mixed nickel-chromium oxide overlayer; (2) growth of submicron-sized oxide nodules; (3) development of dark hole-like patches on the surface; and (4) growth of second generation oxide nodules. Both types of nodules consist primarily of a nickel structure depleted in oxygen. Their formation appears to result from a very rapid outward movement of nickel from localized defects in the metal. The dark patches result from the presence of a chromium oxide-rich underlayer, which appears to form by a lateral migration of chromium from adjacent oxide/metal interface regions and from grain boundaries.     

Redistribution of carbon and oxygen in semicrystalline molybdenum during annealing

Conclusion An increase in the annealing temperature of deformed molybdenum containing 0.011% of interstitial elements in the 1150–1550°C interval effects a steady increase in the amount of carbon and oxygen atoms on the grain boundaries as a result of their segregation from the grain body. After annealing above 1350°C (an average grain size d30 m), the process of the outflow of interstitial elements onto the boundaries takes place incompletely, as a result of which a supersaturated solid solution is formed in the grain body. Subsequent annealing at 1150°C for 4 h leads to an additional increase in the oxygen content and to the formation of molybdenum-carbide particles on the boundaries; this causes a small decrease in the strength characteristics, and a sharp decrease in plasticity characteristics.Institute of Powder Metallurgy, Academy of Sciences of the Ukrainian SSR, E. O. Paton Institute of Electric Welding, Academy of Sciences of the Ukrainian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 28–30, December, 1986.     

Modification of metals and alloys by electron beam treatment (review)

Conclusion Investigations of methods of surface treatment of metals and alloys by a concentrated electron stream are being ever more widely developed. Such action causes a significant change in the structure and properties of materials, which in turn causes a significant improvement in the service properties of the treated parts.Electron beam treatment promotes obtaining of fundamental and practical information on phase and structural transformations in cooling at different rates of materials widely used at present in industry and those having promise of use in the near future. In a number of cases the action of an electron stream provides necessary and unexpected properties of materials.Electron beam heating is used most widely for processes of refining of the surface of metal blanks, hardening of alloys from the liquid and solid states, surfacing and surface alloying, and treatment of previously applied coatings. Methods of amorphisation and shock hardening of thin surface layers are in the study stage.Physicotechnical Institute, Academy of Sciences of the Belorussian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 42–47, July, 1990.