TY - JOUR AB - Al-Li based alloys are attractive materials for the aerospace industry. The twin-roll casting of such materials could provide properties not achievable by conventional direct-chill casting and downstream processing methods due to significantly higher solidification rates. An Al-Li-Cu-Mg-Zr alloy was twin-roll cast with the same alloy containing a small addition of Sc. The microstructure of as-cast materials and the influence of Sc on the behavior of the alloy at elevated temperatures were studied by means of light and electron microscopy and by resistivity measurements. A fine-grained structure was formed during twin-roll casting, but several surface and internal defects were found on the strips, which should be suppressed by a further adjustment of the casting conditions. The addition of Sc had a positive effect on grain size uniformity and microstructure stabilization at elevated temperatures, as shown by the precipitation of a fine dispersion of coherent Sc- and Zr-containing precipitates. AU - Grydin, Olexandr AU - Stolbchenko, Mykhailo AU - Schaper, Mirko AU - Belejová, Sára AU - Králík, Rostislav AU - Bajtošová, Lucia AU - Křivská, Barbora AU - Hájek, Michal AU - Cieslar, Miroslav ID - 24573 IS - 8 JF - Metals SN - 2075-4701 TI - New Twin-Roll Cast Al-Li Based Alloys for High-Strength Applications VL - 10 ER - TY - JOUR AB - Zinc oxide (ZnO) hollow spheres with defined morphology and micro-/nanostructure are prepared by a hydrothermal synthesis approach. The materials possess fine-leaved structures at their particle surface (nanowall hollow micro spheres). Morphology control is achieved by citric acid used as an additive in variable relative quantities during the synthesis. The structure formation is studied by various time-dependent ex situ methods, such as scanning electron microscopy, x-ray diffraction, and Raman spectroscopy. The fine-leaved surface structure is characterized by high-resolution transmission electron microscopy techniques (HRTEM, STEM), using a high-angle annular dark field detector, as well as by differential phase contrast analysis. In-depth structural characterization of the nanowalls by drop-by-drop ex situ FE-SEM analysis provides insight into possible structure formation mechanisms. Further investigation addresses the thermal stability of the particle morphology and the enhancement of the surface-to-volume ratio by heat treatment (examined by N2 physisorption). AU - Engelkemeier, Katja AU - Lindner, Jörg AU - Bürger, Julius AU - Vaupel, Kathrin AU - Hartmann, Marc AU - Tiemann, Michael AU - Hoyer, Kay-Peter AU - Schaper, Mirko ID - 24100 JF - Nanotechnology SN - 0957-4484 TI - Nano-architectural complexity of zinc oxide nanowall hollow microspheres and their structural properties VL - 31 ER - TY - JOUR AB - This experiment studied the strain parameters of rolling an aluminum matrix when wire netting is inserted between aluminum layers. During the experiment, two types of stainless steel fabric netting oriented parallel and diagonal to the rolling axis were placed between two aluminum strips and rolled. Multiple rolling processes were performed in which the temperature and pressure on the material were varied to produce bonding of matrix layers. During the study, the following main investigations were made: strain on areas of longitudinal and transverse cross sections of the composite was measured; stretching and ovalization of net wiring and changes in the net cell angles were determined; mechanical properties of composites along the rolling direction were tested. The main contradiction resulting from this experiment was as follows: the contact pressure required for the bonding of aluminum layers produces extreme tensile strain on the inserted net wires, reducing the mechanical properties of the reinforcing net and thus reducing properties of the entire composite. Optimal results in the longitudinal tension tests were achieved by using strips with diagonally oriented net-reinforcement. AU - Stolbchenko, Mykhailo AU - Makeieva, Hanna AU - Grydin, Olexandr AU - Frolov, Yaroslav AU - Schaper, Mirko ID - 24572 IS - 6 JF - Journal of Sandwich Structures & Materials SN - 1099-6362 TI - Strain parameters at hot rolling of aluminum strips reinforced with steel netting VL - 22 ER - TY - JOUR AU - Wu, Haoran AU - Bill, T. AU - Teng, Z.J. AU - Pramanik, Sudipta AU - Hoyer, Kay-Peter AU - Schaper, Mirko AU - Starke, Peter ID - 41520 JF - Materials Science and Engineering: A KW - Mechanical Engineering KW - Mechanics of Materials KW - Condensed Matter Physics KW - General Materials Science SN - 0921-5093 TI - Characterization of the fatigue behaviour for SAE 1045 steel without and with load-free sequences based on non-destructive, X-ray diffraction and transmission electron microscopic investigations VL - 794 ER - TY - JOUR AU - Tillmann, Wolfgang AU - Lopes Dias, Nelson Filipe AU - Stangier, Dominic AU - Hagen, Leif AU - Schaper, Mirko AU - Hengsbach, Florian AU - Hoyer, Kay-Peter ID - 41521 JF - Surface and Coatings Technology KW - Materials Chemistry KW - Surfaces KW - Coatings and Films KW - Surfaces and Interfaces KW - Condensed Matter Physics KW - General Chemistry SN - 0257-8972 TI - Tribo-mechanical properties and adhesion behavior of DLC coatings sputtered onto 36NiCrMo16 produced by selective laser melting VL - 394 ER - TY - JOUR AU - Andreiev, Anatolii AU - Hoyer, Kay-Peter AU - Grydin, Olexandr AU - Frolov, Yaroslav AU - Schaper, Mirko ID - 41522 IS - 4 JF - Materialwissenschaft und Werkstofftechnik KW - Mechanical Engineering KW - Mechanics of Materials KW - Condensed Matter Physics KW - General Materials Science SN - 0933-5137 TI - Degradable silver‐based alloys VL - 51 ER - TY - JOUR AU - Stolbchenko, Mykhailo AU - Frolov, Yaroslav AU - Makeieva, Hanna AU - Grydin, Olexandr AU - Tershakovec, Michael A. AU - Schaper, Mirko ID - 24571 IS - 18 JF - Mechanics of Advanced Materials and Structures SN - 1537-6494 TI - The mechanical properties of rolled wire-reinforced aluminum composites at different strain values VL - 27 ER - TY - JOUR AU - Tillmann, Wolfgang AU - Hagen, Leif AU - Garthe, Kai-Uwe AU - Hoyer, Kay-Peter AU - Schaper, Mirko ID - 24254 JF - Materialwissenschaft und Werkstofftechnik SN - 0933-5137 TI - Effect of substrate pre‐treatment on the low cycle fatigue performance of tungsten carbide‐cobalt coated additive manufactured 316 L substrates ER - TY - JOUR AB - AbstractDifferent studies have been demonstrated that the surface integrity of substrate bulk materials to be coated has a significant impact on the adhesion of thermally sprayed coatings. It is known that the surface integrity of parts processed by selective laser melting (SLM) differs from those obtained from bulk materials. Although 316L stainless steel is among the most investigated material for SLM, the adhesion of thermally sprayed coatings on 316L stainless steel substrates processed by SLM has not been studied yet. This study aims at evaluating the effect of various mechanical pre-treatments onto 316L stainless steel substrates processed by SLM and their effect on the adhesion of high velocity oxy-fuel (HVOF)-sprayed WC-Co coatings. To differentiate between topographical effects and residual stress-related phenomena, a stress-relief heat treatment of the SLM substrates served as a reference throughout the investigations. The differently pre-treated SLM substrates were investigated with regard to the surface roughness and residual stresses. For the HVOF-sprayed SLM composites, Vickers interfacial indentation tests were conducted to assess the resulting coating adhesion. The findings demonstrated that the HVOF-sprayed WC-Co coatings predominantly exhibit good adhesion to the SLM 316L substrates. However, it was found that the stress state in the SLM 316L substrate surface is more likely to affect the adhesion of the WC-Co coating, while the substrate surface roughness showed a marginal effect. AU - Tillmann, Wolfgang AU - Hagen, Leif AU - Schaak, Christopher AU - Liß, Jan AU - Schaper, Mirko AU - Hoyer, Kay-Peter AU - Aydinöz, Mehmet Esat AU - Garthe, Kai-Uwe ID - 24092 JF - Journal of Thermal Spray Technology SN - 1059-9630 TI - Adhesion of HVOF-Sprayed WC-Co Coatings on 316L Substrates Processed by SLM ER - TY - JOUR AB - AbstractDifferent studies have been demonstrated that the surface integrity of substrate bulk materials to be coated has a significant impact on the adhesion of thermally sprayed coatings. It is known that the surface integrity of parts processed by selective laser melting (SLM) differs from those obtained from bulk materials. Although 316L stainless steel is among the most investigated material for SLM, the adhesion of thermally sprayed coatings on 316L stainless steel substrates processed by SLM has not been studied yet. This study aims at evaluating the effect of various mechanical pre-treatments onto 316L stainless steel substrates processed by SLM and their effect on the adhesion of high velocity oxy-fuel (HVOF)-sprayed WC-Co coatings. To differentiate between topographical effects and residual stress-related phenomena, a stress-relief heat treatment of the SLM substrates served as a reference throughout the investigations. The differently pre-treated SLM substrates were investigated with regard to the surface roughness and residual stresses. For the HVOF-sprayed SLM composites, Vickers interfacial indentation tests were conducted to assess the resulting coating adhesion. The findings demonstrated that the HVOF-sprayed WC-Co coatings predominantly exhibit good adhesion to the SLM 316L substrates. However, it was found that the stress state in the SLM 316L substrate surface is more likely to affect the adhesion of the WC-Co coating, while the substrate surface roughness showed a marginal effect. AU - Tillmann, W. AU - Hagen, L. AU - Schaak, C. AU - Liß, J. AU - Schaper, Mirko AU - Hoyer, Kay-Peter AU - Aydinöz, M. E. AU - Garthe, Kai-Uwe ID - 24255 JF - Journal of Thermal Spray Technology SN - 1059-9630 TI - Adhesion of HVOF-Sprayed WC-Co Coatings on 316L Substrates Processed by SLM ER -