Resource Efficient Material and Forming Technologies

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Authors: Kristina Neh, Madlen Ullmann, Rudolf Kawalla
Abstract: In recent years, magnesium alloys have been received much attention as important structural materials for lightweight components in automotive, electronic and space industries because of the low density, high specific strength, high damping capacities and good casting properties. Among various magnesium alloys, rare earth (RE) containing alloys are known to show high strength, excellent creep resistance, and good thermal stability. Long period stacking ordered structures (LPSO) being responsible for the improved property profile in some Mg–RE alloys. One promising system are the Mg-Y-Zn alloys, which are predominantly processed via extrusion. Only a few studies are focused on hot rolling. However, these works are confined to rolling temperatures between 350 °C and 420 °C. The present paper summarizes the development of a rolling technique including pass schedule and heat treatment for the magnesium alloy Mg-6.8Y-2.5Zn-0.5Al in as-cast condition in order to produce sheets with a final thickness of 2.5 mm. The investigations are accompanied by the characterization of the microstructure as well as the determination of the mechanical properties.
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Authors: Sergey Sidelnikov, Roman Galiev, Andrey Bersenev, Denis Voroshilov
Abstract: At present, Russia is actively developing methods of combined treatment of aluminum alloys, one of which is the method of twin roll casting-extruding. It is very suitable for processing aluminum alloys having a relatively low melting point. The method consists in pouring a melt into the rotating rolls, crystallizing it on the roll surfaces, rolling with a predetermined reduction amount, pressing out in front of the die and squeezing out the product of the predetermined configuration and dimensions through it with drawing ratio in the range of values 10-40. Analysis of technical and economic indicators showed that this method has a number of advantages in comparison with traditional technologies of semicontinuous extruding and continuous casting-rolling. So the output of a good metal at high production volumes can reach 95-97% at a productivity of up to 3-4 tons per hour. In addition, it is possible to quickly move from one profile size to another by changing the matrix. The authors proposed and patented various designs and methods for producing solid and hollow press products from non-ferrous alloys. On their basis, laboratory and pilot-industrial units for combined processing have been created, on which experimental studies have been carried out to obtain long-dimensioned deformed semi-finished products from aluminum alloys series 5xxx, 6xxx, 8xxx and others. The energy-power parameters of the process are determined and found that they are significantly smaller in comparison with traditional technologies (in 10-50 times). Investigations of the mechanical characteristics of press products have been carried out, which showed that when implementing such a treatment scheme, even when producing extruded products from low-plastic alloys, they have a high level of plastic and strength properties. Developed technologies based on the method twin roll casting-extruding now are tested in a laboratory of combined treatment methods in School of Non-ferrous Metals and Material Science in Siberian federal university and industrial conditions of a number of metallurgical plants.
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Authors: Yaroslav Igorevich Kosov, Vladimir Yuryevich Bazhin
Abstract: A novel Al-Er master alloy has been prepared through in situ metallothermic reactions of NaErF4 and aluminium melts. The compound NaErF4 is formed as a result of the interaction of NaF and ErF3 in the melt medium KCl. The metallothermic reactions produce erbium, which through low solubility in molten aluminium and forms intermetallic compound Al3Er. The microstructures of the Al-Er master alloy with different contents of the alloying metal has been investigated. The results showed that the Al-Er master alloy mainly consisted of phases of α-Al and Al3Er, that confirmed by the results of X-ray diffraction. Backscattered electron imaging of the Al-Er master alloy under a scanning electron microscope (SEM) revealed the presence of phase Al3Er, which crystallized in the eutectic composition [Al+Al3Er]. The observed microstructure is explained according to the eutectic reaction in an Al-Er phase diagram. The preparation of Al-Er master alloy by the metallothermic reduction method will allow to reduce energy consumption for master alloy production and to reduce the cost of aluminium alloys alloyed with Er through the novel master alloy.
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Authors: Nikolaus Papenberg, Stefan Gneiger
Abstract: In light of emission reduction and weight saving in transport applications, Mg parts gain alot attention due to their good specific mechanical properties and their low mass. While casting is themain process for manufacturing Mg parts for automotive applications, forged parts show some majorbenefits like superior mechanical properties and absence of porosity. In this work a comparison ofclosed die forged parts made from different Mg-alloys has been carried out. The materials used in thewarm forging process were AZ31 and various Mg-Al-Zn-Ca-Y type (AZXW) alloys. Ca additions areknown to improve the oxidation behaviour and the formability of magnesium alloys, while yttrium isused to enhance the flammability resistance of forged parts. The forgeability, mechanical propertiesand microstructure are analyzed and compared in the present paper.
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Authors: Marie Moses, Claudia Kawalla, Rudolf Kawalla, Michael Höck
Abstract: In order to meet customer requirements, technology developments need to stay focused at process rationalization and quality improvements. Combining the twin-roll casting technology and caliber rolling technology for magnesium wire, customer demands concerning cost-efficiency and high quality can be satisfied. The resulting long products can be applied in the automotive industry and aircraft sector as joining and welding elements or in biomedicine as screws. For this purpose, the paper analyzes potential application fields and their induced quality properties. Special requirements of illustrative magnesium long products are shown by adapting existing requirements of aluminum wire. Finally, the innovative magnesium wire production technology will be explained and the advantages, in particular the resource efficiency, of the developed technology will be discussed.
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Authors: Heike Wemme, Christina Krbetschek, Madlen Ullmann, Anna Freigang, Stefan Plach, Rudolf Kawalla
Abstract: The knowledge about the formation of hot cracking in magnesium alloys, such as in twin-roll cast magnesium sheets and strips, is fundamental for a good quality of the strips during the further processing by rolling or welding and minimize the reject. Hot cracking often occurs in the so-called mushy zone, when solid phases and melt coexist, at temperatures where the material no longer exhibits ductility. For the evaluation of the hot cracking tendency of an alloy, the width of the HTBR (High-temperature brittleness range) can be used. On the basis of a test on a Gleeble HDS-V40, the HTBR was determined for a twin-roll cast AZ31 magnesium alloy. The transition between ductile forming behaviour and complete brittle reaction of the AZ31 alloy is confirmed by the observation of the fracture surfaces (determination of the fracture type) in the scanning electron microscope (SEM) and is located at 555 °C. The HTBR shows a range 35 K.
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Authors: Olexandr Grydin, Mykhailo Stolbchenko, Maria Bauer, Mirko Schaper
Abstract: The industrial application of high-alloyed Al-Mg-Si alloys for the production of thin strips by means of twin-roll casting is limited due to the structural inhomogeneity and segregation formation. To reach the highest mechanical properties of the finished product, a direct influence on the strip formation conditions during the twin-roll casting can be applied. Analogous to the asymmetric rolling process, additional shear stresses were created in the strip forming zone by using different circumferential velocities and torques of the caster rolls. To provide the asymmetric process conditions, only one caster roll was left driven and the second one was left idling during the casting process. The microstructure and the mechanical properties of the strips in the as-cast state as well as after the homogenization and subsequent age-hardening were analyzed. A comparison of the test results showed a positive influence of the asymmetry conditions on the strips’ properties.
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Authors: Vladimir Baranov, Sergey Sidelnikov, Evgeniy Zenkin, Olga Yakivyuk
Abstract: The combination of weldability, corrosion resistance and sufficient strength make it possible to use deformed semi-finished products from the Al-Mg system alloys for sheathing ships' hulls, in car, aircraft and rocket construction, as well as in other areas of industry. To increase the strength characteristics, it is promising to alloy them with small additives of metals such as titanium, zirconium, scandium, and others. In this paper, studies were carried out to obtain deformed semi-finished products (strips, rods and wires) from aluminum alloys in which the scandium content varied from 0.1 to 0.25%. For this purpose, various metal treatment conditions simulated in the laboratory of School of Non-Ferrous Metals and Material Science in Siberian federal university. For the preparation of sheet semi-finished products regimes of hot and cold rolling of a cast billet simulated from a thickness of 40 mm to a thickness of 3 mm. For the preparation of sheet semi-finished products, the modes of hot and cold rolling of the cast billet from a thickness of 40 mm to a thickness of 1-3 mm have been modeled. To produce a welding wire with a size of 2×2 mm, a combined casting and rolling-extruding (CCRE) process was simulated to produce a 9 mm billet and its further rolling in square gauges. Rods with a diameter of 9 mm were produced on a combined processing unit, and wire on a rolling mill with a roll diameter of 130 mm. In accordance with the research program, the mechanical properties of hot-deformed, cold-deformed and annealed sheet semi-finished products were measured. Then the semi-finished products were welded together with the obtained wire and the quality and properties of the welded joint and their corrosion resistance were evaluated. Research results are currently used to develop industrial technologies for the production of sheets and plates from experimental alloys of the Al-Mg system doped with scandium.
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Authors: Robby Lorenz, Hinnerk Hagenah, Marion Merklein
Abstract: Cold forging processes enable the economical production of high quality components like joints, shafts and gears. The manufactured parts are characterized by improved properties such as hardness, surface quality and fatigue strength. For manufacturing components using cold forging, a comprehensive knowledge regarding the cold forging procedure and its process parameters is needed. One important influencing factor, which needs to be analyzed to use the potential of this kind of processes, is the tribological system, especially the used lubricant. The tribological conditions significantly influence the material flow and thus the workpiece quality. Furthermore, resource efficient and environmentally benign metal forming processes became very important within the last decade. The present study evaluates the resulting tribological conditions and their differences for various cold forging lubricants with and without a zinc phosphate based lubricant carrier. The lubricants are based on molybdenum disulphide, polymers, or both inorganic salts and waxes. The tribological conditions of the different lubricants are investigated using the Double-Cup-Extrusion-Test (DCET) as a laboratory friction test.
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