FG Metallische Werkstoffe

20 Items

Recent Submissions
Numerical Investigations on Material Flow During Indirect Extrusion of Copper-Clad Aluminum Rods

Kuhnke, Stefan ; Sanabria, Vidal ; Gensch, Felix ; Nitschke, Renè ; Müller, Sören (2020-06-09)

In the extrusion of clad composite materials with different flow stresses are usually used. This causes an inhomogeneous material flow which can induce sleeve or core fracture. In the present study, the material flow during indirect extrusion of copper-clad aluminum (CCA) rods was analyzed by means of experimental and numerical investigations throughout the process. In order to provide material...

Röntgenographische Analysen der Umformmechanismen und der Eigenspannungen umgeformter Bleche im Single Point Incremental Forming-Verfahren

Dobecki, Mateus (2020)

Die inkrementelle Blechumformung ist ein flexibles Fertigungsverfahren zur Herstellung komplex geformter Teile durch die kontrollierte Bewegung des Umformwerkzeugs. Die mechanischen Eigenschaften inkrementell umgeformter Bleche im Single Point Incremental Forming (SPIF)-Verfahren werden maßgeblich von den wirkenden Umformmechanismen während der Herstellung beeinflusst. In der vorliegenden Arbei...

Extrusion of Aluminum Tubes with Axially Graded Wall Thickness and Mechanical Characterization

Negendank, Maik ; Müller, Sören ; Reimers, Walter (2014-08-25)

In this study the indirect extrusion of seamless aluminum tubes with variable wall thickness was investigated. Therefore, an axially moveable stepped mandrel was applied. Investigations revealed that wall thickness transitions can either be graded over the tube length or very sharp. The microstructures in thin-walled and thick-walled tube sections were investigated. The local variation of the e...

Influence of choked angle of bearing channel on profile grain structure during multi-hole extrusion of aluminum alloy

Müller, Sören ; Sanabria, Vidal (2018-08-11)

Direct extrusion of aluminum alloy EN AW-6060 was carried out applying a four-hole die with pair-wise parallel and choked long channels. Due to the dissimilar friction inside parallel and choked channels profiles with different length were extruded simultaneously. In order to investigate the grain structure evolution along the whole extrusion process, multiple sections from the beginning to the...

Application of Friction Shear Test for Constitutive Modeling Evaluation of Magnesium Alloy AZ31B at high Temperature

Sanabria, Vidal ; Gensch, Felix ; Müller, Sören (2020-04-26)

The experimental determination of the flow stress and its mathematical formulation are essential for the numerical simulation of metal forming processes. The hot compression test is widely used to analyze the flow stress evolution as function of temperature, strain and strain rate. The compression test is limited to a relative low strain (ε≤1) which is acceptable when the stress is minor influe...

Microstructure Evolution of Friction Boundary Layer during Extrusion of AA 6060

Sanabria, Vidal ; Müller, Sören ; Reimers, Walter (2014-10-14)

The tribological behavior between the aluminium alloy AA 6060 and the hot working steel 1.2344 has been recently studied using a new axial friction test for extrusion processes. With this new test, the friction forces as well as the specimens’ plastic deformations generated during sliding tests can be investigated. Selected specimens tested at high temperature (300-500 °C), normalized normal st...

Backward rod extrusion of bimetallic aluminum-copper alloys at room temperature

Sanabria, Vidal ; Gall, Sven ; Gensch, Felix ; Nitschke, René ; Müller, Sören (2019-07-02)

The backward rod extrusion of bimetallic aluminum-copper alloys at room temperature was investigated. The aluminum alloy EN AW-1080A and the copper alloy Cu-ETP were selected to prepare the core and sleeve of the billet respectively. The copper cross section was equivalent to 30% of the billet. Moreover, the billet was extruded applying a conic die angle of 90° and an extrusion ratio of 14:1. E...

Extrusion of magnesium alloy hollow profiles with axial variable wall thickness

Negendank, Maik ; Sanabria, Vidal ; Müller, Sören ; Reimers, Walter (2019-07-02)

Industrially extruded profiles are characterized by a constant cross section along the length since rigid dies are applied in the process. However, if it would be possible to extrude profiles with cross sections that can be locally adapted (tailored) to the acting forces or stresses this would mean a significant potential for weight and material savings. Hence, in this study the extrusion of ma...

Analysis of the flow imbalance on the profile shape during the extrusion of thin magnesium sheets

Gall, Sven ; Müller, Sören ; Reimers, Walter (2013-12-31)

The extrusion process facilitates the production of magnesium sheets featuring a very thin thickness as well as excellent surface properties by using a single process step only. However, the extrusion of the magnesium sheets applying not optimized process parameters, e.g. low billet temperature or/ and poorly deformable magnesium alloy, produce pronounced buckling and waving of the extruded she...

Modification of the anisotropy and strength differential effect of extruded AZ31 by extrusion-shear

Jähnke, Martin ; Gensch, Felix ; Müller, Sören (2018-05-03)

The extrusion of magnesium alloys results in a pronounced fiber texture in which the basal planes are mostly oriented parallel and the c-axes are oriented perpendicular to the extrusion direction. Due to this texture the Strength Differential Effect (SDE), which describes the strength difference between tensile and compression yield strength, and the elastic anisotropy in the sheet plane are ob...

Influence of temperature and sliding speed on the subsurface microstructure evolution of EN AW-6060 under sticking friction conditions

Sanabria, Vidal ; Müller, Sören (2017-10-16)

The microstructure evolution of the friction boundary layer of the aluminum alloy EN AW-6060 was investigated. Sticking friction tests at different temperatures and sliding speeds were carried out. A severe deformation below the friction surface was observed by means of LOM and EBSD mapping. Thus, the thickness variation and the grain structure of the high deformation zone could be described. F...

Influence of the Microstructure and Silver Content on Degradation, Cytocompatibility, and Antibacterial Properties of Magnesium-Silver Alloys In Vitro

Liu, Zhidan ; Schade, Ronald ; Luthringer, Bérengère ; Hort, Norbert ; Rothe, Holger ; Müller, Sören ; Liefeith, Klaus ; Willumeit-Römer, Regine ; Feyerabend, Frank (2017-06-22)

Implantation is a frequent procedure in orthopedic surgery, particularly in the aging population. However, it possesses the risk of infection and biofilm formation at the surgical site. This can cause unnecessary suffering to patients and burden on the healthcare system. Pure Mg, as a promising metal for biodegradable orthopedic implants, exhibits some antibacterial effects due to the alkaline ...

Processing Effects on the Formability of Magnesium Alloy Sheets

Bohlen, Jan ; Cano, Guadalupe ; Drozdenko, Daria ; Dobron, Patrik ; Kainer, Karl ; Gall, Sven ; Müller, Sören ; Letzig, Dietmar (2018-02-23)

As a generalized semi-finished product, the use of magnesium sheets requires addressing two major aspects of their processing: their microstructure and texture control, which are both essential for the forming behavior of such sheets during their forming to parts. Further, the processing of such sheets is complex, and therefore expensive, and requires simplification. In this work, magnesium all...

Untersuchung magnetischer Streufelder in einem inhomogen verformten Baustahl mittels passiv-magnetischer Prüfverfahren

Sonntag, Nadja (2019)

Die Metal Magnetic Memory (MMM) Methode ist ein standardisiertes, zerstörungsfreies Prüfverfahren, das für die Detektion von lokal geschädigten Materialbereichen in ferromagnetischen Bauteilen oder Proben verwendet wird. Es basiert auf der Annahme lokaler magnetoelastischer Wechselwirkungen an Spannungskonzentrationsstellen, die schwache magnetische Streufelder an den geschädigten Prüfkörper¬ob...

Grundlegende Charakterisierung des Strangpressprozesses pressnahtbehafteter Magnesium - Hohlprofile

Gensch, Felix (2019)

Durch das Strangpressen von Magnesiumwerkstoffen über Kammerwerkzeuge lassen sich komplexere Hohlprofilgeometrien darstellen als durch Verwendung eines Dornes. Jedoch beinhalten so hergestellte Pressprodukte zumeist zwei oder mehrere Längspressnähte, die sich in der Mikrostruktur und daher den mechanischen Eigenschaften lokal vom umgebenden Gefüge unterscheiden können. Daher ist eine Untersuchu...

Creep behavior of a γ′-strengthened Co-base alloy with zero γ/γ′-lattice misfit at 800 °C, 196 MPa

Midtlyng, Jan ; Epishin, Alexander I. ; Petrushin, Nikolay V. ; Link, Thomas ; Nolze, Gert ; Svetlov, Igor L. ; Reimers, Walter (2017)

Deformation and structural behavior of an experimental γ′-strengthened Co-base alloy during creep at 800 °C and 196 MPa have been investigated. The characteristic features of this alloy are zero γ/γ′-lattice misfit and a fine γ/γ′-microstructure. In the initial condition, the γ′-precipitates in this alloy are small (size of about 100 nm), have polyhedral morphology, and are separated by the ver...

Exploiting the features of energy-dispersive synchrotron diffraction for advanced residual stress and texture analysis

Genzel, Ch. ; Denks, I. A. ; Coelho, R. ; Thomas, D. ; Mainz, R. ; Apel, D. ; Klaus, M. (2011)

Responding to a growing interest from the materials science community for residual stress, texture, and microstructure analysis, strong efforts are made to enhance existing and develop novel methods that allow for fast in-situ studies at elevated temperature, measurements under external load, or residual strain, and stress scanning with high spatial resolution. In the paper, energy-dispersive d...

Analyse der Mikrostrukturentwicklung von CuInSe2 mittels in-situ Röntgenbeugung

Stange, Anna Helena (2018)

Die Reduzierung der Absorberschichtdicke auf wenige Mikrometer eröffnet neue Anwendungsmöglichkeiten für die Photovoltaik. Der Verbindungshalbleiter Cu(In,Ga)Se2 (CIGSe) hat sich als besonders geeignet für solche Dünnschichtsolarzellen herausgestellt. Mit CIGSe-Absorbern aus einem mehrstufigen Syntheseprozess werden die bisher höchsten Effizienzen im Bereich der Dünnschichttechnologie erreicht....

Preparation, characterization and electrical properties of nanocomposites based on hyperbranched polymers

Omara, Shereen Said Shabaan (2018)

Nanocomposites based on hyperbranched polymers (HBPs) and layered silicates as nanofillers are a relatively new class of nanocomposites. Due to their unique physical/chemical properties, they have attracted scientific interests. This study provides to a better understand the structure-dynamics-properties relationship, for different types of HBP/ kaolinite (Ka) nanocomposites. Two different me...

Annihilation of structural defects in chalcogenide absorber films for high-efficiency solar cells

Mainz, Roland ; Sanli, Ekin Simsek ; Stange, Helena ; Azulay, Doron ; Brunken, Stephan ; Greiner, Dieter ; Hajaj, Shir ; Heinemann, Marc D. ; Kaufmann, Christian A. ; Klaus, Manuela ; Ramasse, Quentin M. ; Rodriguez-Alvarez, Humberto ; Weber, Alfons ; Balberg, Isaac ; Millo, Oded ; Aken, Peter A. van ; Abou-Ras, Daniel (2016)

In polycrystalline semiconductor absorbers for thin-film solar cells, structural defects may enhance electron-hole recombination and hence lower the resulting energy conversion efficiency. To be able to efficiently design and optimize fabrication processes that result in high-quality materials, knowledge of the nature of structural defects as well as their formation and annihilation during film...