Band 53, Heft 10

Kurzfassung Mit der Veröffentlichung der DIN EN ISO 6892-1:2009 [1] wurde für den Zugversuch bei Raumtemperatur eine Harmonisierung der in Europa verbindlichen EN 10002-1:2001 [2] mit der ISO 6892:1998 [3] erreicht. Wesentliche Änderungen sind die Einführung der Dehngeschwindigkeit und der Dehngeschwindigkeitsregelung als maßgebliche Prüfgeschwindigkeit bzw. Regelungsart, als Verfahren A bezeichnet. Mit der korrekten Anwendung dieses Verfahrens wird gewährleistet, dass im Moment der Kennwerteermittlung bei enger spezifizierten zulässigen Dehngeschwindigkeitsbereichen vergleichbare resultierende Dehngeschwindigkeiten an der Probe auch bei unterschiedlichen Steifigkeiten der Prüfaufbauten vorliegen. Dieses führt besonders bei dehngeschwindigkeitssensitiven Werkstoffen zu deutlich vergleichbareren Ergebnissen. In diesem Beitrag wird auf die Notwendigkeit der Einführung des Verfahrens A, der möglichen Umsetzungen auch bei Verwendung von älteren Prüfsystemen sowie exemplarisch auf vergleichende Ergebnisse der Verfahren an einem dehngeschwindigkeitssensitivem Stahlwerkstoff eingegangen.

With the publication of EN ISO 6892-1:2009 [1], the harmonisation of tensile testing at room temperature in Europe was achieved by combining EN 10002-1:2001 [2] with ISO 6892:1998 [3]. Essential changes are the introduction of the strain rate and the strain rate control as the significant testing rate or control mode, respectively, referred to as “Method A”. By using this method in the correct way it is guaranteed that in the moment of determination of properties comparable resulting strain rates at the test piece in smaller ranges of specified strain rates are adopted — also if different stiffnesses of the testing equipment are present. This leads especially for strain rate sensitive materials to better comparable results. In this paper it is documented the need for the implementation of method A, methods for the realisation — also by the use of older testing systems — and an example of the comparability of results of the methods for a strain-rate-sensitive-steel.

The refinement of the weld metal grain structure may lead to a significant change in its mechanical properties and in the weldability of the base metal. One possibility to achieve weld metal grain refinement is the inoculation of the weld pool. In this study, it is shown how additions of titanium and boron influence the weld metal grain structure of GTA welds of the aluminium alloy 5083 (Al Mg4.5Mn0.7). For this purpose, inserts consisting of base metal and additions of the master alloy Al Ti5B1 have been cast, deposited in the base metal and fused in a GTA welding process. The increase of the Ti and B content led to a significant decrease of the weld metal mean grain size and to a change in grain shape. The results provide a basis for a more precise definition of the chemical composition of commercial filler wires and rods for aluminium arc welding.

In order to close one of the microprobe ends covering, considering geometrical sizes and the properties of the material, the electro riveting process by TIG welding was chosen. The semi spherical shape of the end closed by welding supposed a pre-preparation of the end and an adequate positioning of gun and covering so that the material burning was avoided and the process automatically developed. Macroscopic investigations related to the geometrical shape of the closed end allowed the optimization of the welding process and the structural investigations made by optical microscopy and X-rays diffraction evinced the structural transformations of the material, supplying information for the post welding heat treatment to increase the corrosion resistance characteristics of the covering.

Kurzfassung In Kooperation zwischen dem Institut für Kunststoffverarbeitung (IKV) und der Bundesanstalt für Materialforschung und -prüfung (BAM) wurde das mechanische Verhalten unter Druck- und Zugbelastung unterschiedlicher morphologischer Strukturen teilkristalliner Thermoplaste (PP und POM) untersucht. Im Ergebnis steigt der E-Modul sowohl der druck- wie auch zugbelasteten Prüfkörper aus spritzgegossenem PP und POM mit gröberem Gefüge an. Probekörper mit scherinduziertem Gefüge zeigen einen hohen Einfluss des Kristallisationsgrads auf den E-Modul.

The Crucible Method is a standard method to determine the corrosion between slag and refractory. According to this method refractory samples are heated to experimental temperature with the active slag powder inside the crucible. The aim of the experiment is to corrode the refractory by slag penetration and cutting the refractory to analyze the corroded surface to determine the slag-refractory interaction. In this study, this method was used and supported by a computer aided surface analyze system which recently has several application areas in material science. The image of the corroded surface of the refractory was transferred to a computer. Image settings and calibrations of complex shaped slag penetration areas were done by Photoshop. Quantitative analysis was done by MVH-ImagePCv7 image analysis software. It was found that the qualitative and quantitative analysis of the Crucible Method was enhanced by the help of computer aided surface display and image analysis techniques.

Harmful effects of thermal oxides formed on austenitic stainless steels (SS) like AISI 304 and 316L by heating in air or other oxidizing gases on their pitting liability in chloride solutions have been studied by pursuing geometric characteristics of corrosion process (pits density, their depths, and mouth areas, ie. penetrating and superficial detrimental consequences etc.). The possibility of preventing the decay of thermally oxidized austenitic SS by chemical removal (pickling) of oxides before exposure to chloride solutions was successfully applied on simple specimens but serious difficulties arose on welded parts and on parts exposed to other temperature gradients during manufacture or in exploitation.

Kurzfassung Im Rahmen des Niedersächsischen Innovationsverbunds Plasmatechnik (NIP) werden neue Anwendungen der Plasmatechnologie in den Bereichen Fertigungstechnik und Materialanalyse bis hin zur Medizintechnik erschlossen sowie ihr ökonomischer und ökologischer Nutzen evaluiert. Im Bereich der Materialanalyse zählt dazu die Entwicklung eines spektroskopischen Verfahrens unter Nutzung eines ökoeffizienten Atmosphärendruckplasmas zur Emissionsanregung. Zum Einsatz kommt hierbei eine im Rahmen des Projekts entwickelte neuartige Plasmaquelle, die für die Analyse gasförmiger, flüssiger und fester Proben in unterschiedlichen Modi betrieben werden kann. Der Energieeintrag in das Probenmaterial durch diese Plasmaquelle beträgt hierbei wenige Mikrojoule. An verschiedenen Probenmaterialien wurde gezeigt, dass sich dieses Verfahren zur Erzeugung und Detektion elementspezifischer Spektrallinien eignet.

Kurzfassung Die Walzversuche von dünnen Stahlfolien in einem 20-Walzen-Sendzimirgerüst mittels Arbeitswalzen aus Hochleistungskeramik ergaben durchweg eine hervorragende Anwendbarkeit dieser Werkstoffe, bei denen zu erwarten steht, dass die Anwendung von keramischen Walzen wegen erhöhter Standzeit deutlich günstiger sein wird.

In this study, the properties, applications, technological barriers, and future projection of magnesium and magnesium based materials in fuel economy and energy production were evaluated. Mg lowers fabrication and joining costs, substitution by lightweight materials enable weight savings, in addition lifetime fuel costs and CO 2 emission are reduced. Studies state that reducing the automotive weights by a certain amount will result in a similar reduction in fuel consumption and CO 2 emissions. Most power systems, either renewable or nuclear, provide solutions for electricity production, but to date, there is no satisfactory substitute for liquid fossil fuel for use in transportation (cars, airplanes, and the like) due to environmental reasons or security of supply. A resent approach to this problem is to use hydrogen as fuel. Researches on Magnesium-Air Fuel Cell (MAFC) Technology resulted in new and improved technologies which have advanced the magnesium-air fuel cell to commercialization. The MAFC approach to an alternative energy source is the development of a powerful, reliable and environmentally friendly non-toxic fuel cell that generates energy using magnesium. From the results of the resarches it is concluded that magnesium applications reduce CO 2 emission, and fuel costs.

The joining of Nodular Cast Iron with the conventional methods presents many problems due to the presence of high carbon content and low ductility. Therefore it is necessary to use heat treatment or to take some precautions before and after bonding. In this study, the graphite distribution on both sides of the interface of diffusion bonding of the AISI 1030 low carbon steel with Nodular Cast Iron was investigated. In order to observe the behavior of the graphite nodules in diffusion bonding, AISI 1030 was used as the comparison of alloy. Diffusion bonding experiments were carried out in an argon atmosphere at the temperatures of 900–950 and 1000 °C and 15 MPa under a dynamic load for 50–100 and 150 min. holding times. The properties of microstructure and graphite distribution that formed in the interface zone of the joints were examined by optic microscope, SEM, EDS, and X-Ray analysis. The hardness values from the interface were measured with the HV hardness scale. The strength of the joint was tested by lap-shear tests. The result of all observations indicated a homogenous graphite distribution. On the other hand, as a function of the process temperature elevation, an increase in the amount of graphite atoms that migrated towards the interface and a decrease in the nodule diameters were observed.