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The present work summarizes the most important results of a research project dealing with the comprehensive investigation of the bonding mechanisms between cold-sprayed Al coatings and various poly- and monocrystalline ceramic substrates (Al2O3, AlN, Si3N4, SiC, MgF2). Due to their exceptional combination of properties, metallized ceramics are gaining more and more importance for a wide variety of applications, especially in electronic engineering. Cold spray provides a quick, flexible, and cost-effective one-step process to apply metallic coatings on ceramic surfaces. However, since most of the existing cold-spray-related publications focus on metallic substrates, only very little is known about the bonding mechanisms acting between cold-sprayed metals and ceramic substrates. In this paper, the essential factors influencing the bonding strength in such composites are identified. Besides mechanical tensile strength testing, a thorough analysis of the coatings and especially the metal/ceramic interfaces was conducted by means of HRTEM, FFT, STEM, EDX, EELS, GAXRD, and EBSD. The influence of substrate material, substrate temperature, and particle size is evaluated. The results suggest that, apart from mechanical interlocking, the adhesion of cold-sprayed metallic coatings on ceramics is based on a complex interplay of different mechanisms such as quasiadiabatic shearing, static recrystallization, and heteroepitaxial growth.

Carbon fibre reinforced carbon composites (C/C) are characterised by their excellent thermal, chemical and mechanical properties. The intrinsic porosity and fibre reinforcement grant them an excellent damage tolerance. The production of complex structures is time consuming and very expensive. An innovative approach to this topic is the integration of simple geometric ceramic composite materials within complex polymer structures. The motivation of this contribution is to investigate the influence of hexamethylenetetramine as hardener (hardener content: 4, 8, 12 and 16 %) and curing parameters (tempered and non-tempered) on the microstructure and mechanical properties of the porous C/C composites. During the course of this contribution, selected carbon fibre reinforced polymer (CFRP) composites with different porosities were produced while adjusting the resin or hardening agent-ratio, as well as the processing parameters. Subsequent to the curing of the CFRP samples, porous C/C composites were produced by means of a pyrolysis process. The final part of the contribution is comprised of the microstructural analysis by light microscopy and the explanation of the flexural strengths, by utilising a “three-point-bending test”.

Cold gas sprayed Al coatings deposited onto wurtzitic AlN substrates show excellent adhesion. As a possible adhesion mechanism, the local heteroepitaxy between Al and AlN was considered and verified experimentally in Al coatings, which were deposited using magnetron sputtering or cold gas spraying on single-crystalline and polycrystalline AlN substrates. Analysis of the local orientation relationships at the Al/AlN interfaces revealed that preferentially such lattice planes of Al align parallel with the upright lattice planes of AlN, which possess similar interplanar distances. The matching lattice planes in the Al coatings grew as continuations of the lattice planes in the AlN substrates. In all samples under study, the parallel alignment of the lattice planes {220} Al and {110} AlN was found. Additional orientation relationships between Al and AlN arose if parallel lattice planes with similar interplanar spacing could be found in both counterparts via rotation of the lattice planes {220} Al around their normal direction. Still, the oriented growth of Al on AlN is only possible if Al atoms in the deposited coatings are mobile enough to rearrange along the AlN surface. Whereas the mobility of Al atoms in a magnetron sputtering process is expected to be sufficiently high, the intrinsic mobility of Al atoms in the cold gas sprayed particles is anticipated to be low. However, the auxiliary microstructure analyses have shown that local recrystallization and partial melting are two phenomena, which can facilitate the rearrangement of Al atoms within the cold gas sprayed coating.

Suitable joining technologies are necessary for the application of aluminum matrix composites (AMC). Especially dissimilar joints between AMC and stainless steel are of enhanced interest. In this work, the approach of arc brazing source of this material combination is investigated. Therefore, basic examinations like the wetting behavior of a developed filler on the base metals is realized. The used filler of the system Al-Ag-Cu show a ternary eutectic of the phases Ag2Al, Al2Cu, and solid solution of Al. Sessile drop technique is applied for the wetting tests. To generate the arc, a TIG welding unit is used. The results of these wetting tests, like the wetting angles and the microstructure of the interfaces, are described and discussed. The wetting angle measured on cross sections show that the wetting on AMC is good (< 30°) while the wetting on stainless steel (~ 90 °) has to be improved. That demonstrates the excellent wettability of the AMC and the suitability of that approach. The wettability of stainless steel can be improved by pretreating, like preheating and polishing, which results in a wetting angle of approx. 35°. The influence of these pretreatments on the microstructure due to a various diffusion behavior of, for example, Al at the interface of the combined materials are described. Different phases in comparison to the filler can be seen at the interfaces of braze metal and the base metals by using SEM, due to a strong diffusion of Al. Analyze by energy-dispersive x-ray spectroscopy (EDXS) and x-ray diffraction (XRD) at the interface of braze metal to stainless steel indicate intermetallic layers of the system Fe-Al, like AlFe3, Al2Fe and Al13Fe4. In the case of the AMC, a solid solution of Al in shape of a not compact layer occurs and no formation of Al4C3 can be detected.

Co-based materials are widely used in high temperature applications like aircraft industry, industrial furnaces, or gas turbine manufacturing. The main requirements on the Co superalloys are high temperature and corrosion resistance. To produce complex structures, it is necessary to join these alloys. In this work, Co-based brazing fillers for high temperature service conditions are developed. The influence of different alloying elements on the melting behavior as well as on the microstructure is investigated. A melting temperature below 1200 °C is achieved via addition of Ti to the near eutectic alloy CoZrTaC9, developed in previous studies. Brazing tests are carried out on the Co-based superalloy Mar M 509 using induction heating. The mechanical properties are determined by tensile tests at room temperature and at an elevated temperature of 850 °C. The fracture morphology of the tensile samples is investigated by light microscopy as well as SEM.

Nanoparticles exhibit a decrease in sintering and melting temperature with decreasing particle size in comparison to the corresponding bulk material. After melting or sintering of the nanoparticles, the material behaves like the bulk material. Therefore, high-strength and temperature-resistant joints can be produced at low temperatures, which is of big interest for various joining tasks. Joints (substrate: Cu) were prepared with an Ag nanoparticle-containing paste. The influence of the adjustable process parameters joining pressure, joining temperature, holding time, heating rate, thickness of paste application, surface treatment, pre-drying process, and subsequent heat treatment on the strength behavior of the joints was investigated. It is shown that in particular, the joining pressure exerts an essential influence on the achievable strengths. In addition, temperature, holding time, and thickness of paste application have a significant effect on strength behavior. In contrast, the pre-drying process, heating rate, surface pre-treatment, and subsequent heat treatment possess hardly any influence on joint strength.

This article focuses on the development of phenolic resin moulding materials for the production of new carbon fibre-reinforced ceramic composite materials based on C/C-SiC by utilising the LSI (liquid silicon infiltration) production method. The production of these moulding materials is being accomplished by combining phenolic resin and carbon fibres with the addition of a few selected parts of processing aids, during which the influence of the used lubricants on the processability of the moulding materials is examined. The starting materials, microstructures and mechanical properties of the materials were characterised at every step of the entire process (CFRP and C/C composites) as well as the end of the whole production (C/C-SiC composites). During this investigation a link between the portions of the lubricant used, the forming of the porosity and the impact on the mechanical properties was discovered. In regards to the optimisation of the process the involved parties were able to determine an optimal lubricant ratio.

Fibre-reinforced ceramic composite materials offer excellent thermal, mechanical and chemical properties. Due to their intrinsic fibre structure and porosity, they offer a great damage tolerance. Therefore, they provide superb attenuation characteristics, as do polymer composites. The current compound systems consisting of ceramic components feature a rather low capacity for energy absorption in relation to their weight; this is a fact in dire need of a fundamental change. In regards to the development of new hybrid ceramic/polymer material compounds basic research of the material design and binding behaviour of the different components is necessary. The advantage of this development allows for a selective implementation of positive characteristics of one component in an integrated compound-system. This opens up completely new possible are-as of application, such as wear and tear resistant and chemically inert, energy absorbing elements for the construction of reactors or areas of medical technology. During the investigation, a few selected fibre-reinforced ceramic composite materials with a specific porosity were produced, while adjusting the amount of resin/hardening agent used, as well as modifying other parameters. This was followed by tests regarding the wetting with a polyurethane component. The characterisation and analysis of the hybrid compounds on a microscopic scale is achieved by means of optical microscopic examinations. The characterisation of the mechanical attenuation characteristics on the other hand is realised by means of DM(T)A. The flexural strength is determined by utilising a “three-point-bending test”.

Sandwich structures consist of one light core layer and two top layers, which form the load-bearing structure. These layers have to be stiff and strong and have to protect the structure against indentations. The main task of the core layer is to keep the top layers in place and to generate a high shear stiffness. In order to obtain the required space between the top layers, the core layer has to have a high specific volume. Different sandwich materials with aluminium or steel top layers and cores of aluminium combs, corrugated aluminium sheets or aluminium foams are already known. In order to obtain better properties in terms of strength fibre-reinforced plastics (FRP) are utilised as top layers; this is the focus of numerous of the current research studies. The sole use of these materials leads to negative effects regarding the damage and impact behaviour. New top layers with high strength and high stiffness characteristics as well as good damage tolerances are to be expected by utilising metal layers in combination with endless fibre-reinforced plastics, so called hybrid laminates. These hybrid laminates combine the positive properties of metals (e.g. ductility) and fibre-reinforced plastics (e.g. tensile strength). The focus of this investigation lies on the production and characterisation of sandwich structures with aluminium foam core layers and hybrid laminate top layers. The foam cores consist of closed pore aluminium foams produced by utilising ingot and powder metallurgical techniques. The top layers consist of glass fibre-reinforced thermoplastics and aluminium layers. The production of the sandwich materials is realised by means of thermal pressing.

The properties of fibre-reinforced composites depend on the interface between the matrix and the fibre. The surface of the fibres plays a key role in the load transmission. In this article, a method based on scanning electron microscopy images of fibre cross sections is introduced to quantify the surface roughness. By utilising an image editing software to get a digital profile of the fibre contour, the arithmetic roughness Ra of a carbon fibre was calculated. The method was tested on a C-fibre with a diameter of 7 microns and compared with the images of an atomic force microscopy (AFM). The method allows a comparison of different types of fibres as well as an investigation regarding the influence of fibre treatments.

Hybrid laminates combine the positive properties of metals and fibre reinforced plastics. Thereby, the relatively free selectable components provide further benefits. Especially thermoplastic matrices offer positive aspects like the possibility of deformation, recyclability as well as the possibility of mass production. To obtain such hybrid laminates the first step is the production of pre-consolidated unidirectional endless fibre reinforced thermoplastic foils. In a second step, these pre-impregnated fibre-foil tapes were alternating thermally pressed with metallic layers in tailored compositions. To use the full capacity of the hybrid laminates an adequate interface between the fibre reinforced thermoplastics and the metallic foil is essential. Different investigations of the authors display the principle possibility to produce hybrid laminates with carbon endless fibre reinforced thermoplastics and aluminium alloy foils. Nevertheless, load free delamination’s occurs. The reason for these delaminations within the interface of the fibre reinforced thermoplastics and the metallic foil are the differences in the thermal expansion coefficient of the components. Caused by the consolidation at elevated temperatures these differences become more significant and reduce the reproducibility of the hybrid laminates. To minimize these thermal induced stresses the graduation of the thermal expansion coefficient is one possibility. This graduation is possible by utilising glass fibre thermoplastic tapes between the aluminium alloy foil and the carbon fibre reinforced thermoplastics. Further investigations are dealing with so called expansion alloys to adapt the thermal expansion coefficient. The latter approach provides the benefit to utilize the full mechanical properties of the carbon fibre reinforced thermoplastics and to economize the glass-fibre tapes. Nevertheless, these expansion alloys are characterized by a high density. Hence, within this contribution the specific mechanical properties as well as the advantages and disadvantages of hybrid laminates with expansion alloys or aluminium alloys with glass-fibre thermoplastics interlayers are discussed and assessed. These specific mechanical properties display the potential of the expansion alloy in spite of the high density by means of comparable values. The sample only consisting of carbon fibre reinforced plastics highlights the great variety and possibilities of different hybrid laminate structures and combinations regarding the thickness and positioning of the component layers.

Hybrid laminates with thermoplastic matrices offer clear advantages over laminates based on thermosetting resins. These include the formability, recyclability as well as the suitability for mass production, to name a few. The inline integration of smart systems like sensors and actuators in the hybrid laminates during the hot-pressing process is one of the long-term objectives of the Federal Cluster of Excellence MERGE. This work aims to deposit Ni-C thin films by dc magnetron sputtering on polyimide substrates for the application as strain sensors in hybrid laminates. During the first step hybrid laminates containing different polyimide foils were prepared by hot-pressing, this was followed by the mechanical testing and selection of the most suitable polyimide substrate for the Ni-C thin film deposition. The second part consisted of depositing Ni-C thin films by means of dc magnetron sputtering and utilising different Ni-C plug targets. The films were characterised regarding their growth rate, composition, structure and temperature coefficient of electrical resistance.

The increasing implementation of fibre-reinforced plastics (FRP) leads to a broad utilization of metal/FRP joints. The examination of adhesively bonded metal/FRP joints is focusing on the maximum joint strength and the surface pretreatment used to promote it. A deeper understanding of the mechanisms behind the correlation is lacking. Along with the chemical condition of the surface (free chemical bonds, polarity, etc.) the surface morphology plays an important role. This study addresses the connection between the surface morphology and joint strength. The investigation of the surface morphology of the metallic joining area and the fractured surface of both joining partners by means of imaging and tactile methods and the results are presented.

We investigate the influence of the chemical composition and modes of spraying of electric-arc coatings from powder wires of the Stein-Mesyfil series, in particular, 953V, 932V, 954V, and 957V, on their abrasive wear resistance and corrosion characteristics. It is established that all coatings obtained at a current of arc burning of 350 А, have the smallest porosity and largest resistance to abrasive wear resistance, and coatings obtained from 932V and 957V wires are most wear resistant. An influence of the chemical composition and spraying modes on the electrochemical properties of the coatings in a 3% solution of sodium chloride is not found.

Brazing has a long tradition at the Institute of Material Science and Engineering of the University of Chemnitz, Germany. During the last years, comprehensive and innovative knowledge in brazing and soldering technologies were generated. Originating from high-temperature brazing, topics like metal-ceramic and light metal brazing, ultrasound assisted joining processes through to brazing of metal matrix composites were examined. In addition, new topics like joining by nanoparticles or corrosion behavior of brazed heat exchangers are in the focus of research. Prof. Bernhard Wielage managed the institute for 22 years. Today, Prof. Guntram Wagner introduces new topics like friction stir welding and continues the activities in brazing. Trendy badawcze w procesach lutowania miękkiego i twardego Streszczenie Tradycje związane z tematyką lutowania twardego w Instytucie Materiałoznawstwa i Inżynierii Uniwersytetu w Chemnitz (Niemcy) są długie. W ciągu ostatnich lat wygenerowano kompleksową i innowacyjną wiedzę dotyczącą technologii lutowania miękkiego i twardego. Zajmowano się problematyką badawczą wywodzącą się od lutowania wysokotemperaturowego, taką m.in. jak: lutowanie twarde metali lekkich z ceramiką i wspomaganie procesu spajania ultradźwiękami w lutowaniu kompozytów metalowych. Obecnie przedmiotem badań są nowe zagadnienia, takie jak: spajanie nanocząsteczkami oraz zachowanie odporności korozyjnej wymienników ciepła lutowanych na twardo. Profesor Bernhard Wielage zarządzał Instytutem przez ostatnie 22 lata. Obecnie, nowy Dyrektor Instytutu Profesor Guntram Wagner zajmuje się takimi zagadnieniami, tjak np. zgrzewaniem tarciowym z wymieszaniem materiału zgrzeiny (FSW) i kontynuuje prace badawcze związane z lutowaniem twardym.

Die Metallisierung von Keramiken mittels Kaltgasspritzens stand im Fokus zahlreicher Veroffentlichungen der jungeren Vergangenheit. Die Haftmechanismen metallischer Schichten auf nicht-duktilen Substraten sind jedoch noch nicht vollkommen verstanden. Fruhere Untersuchungen von Titan-Schichten auf Aluminiumoxid ergaben, dass eine Kombination von durch adiabatische Scherprozesse induzierten Rekristallisationsvorgangen und heteroepitaktischem Wachstum dafur verantwortlich sein konnte, dass kaltgasgespritzte Schichten auf atomar glatten Keramiksubstraten hohe Haftfestigkeiten erreichen. Die vorliegende Arbeit zielt auf die Untersuchung des Interfacebereichs kaltgasgespritzter Aluminiumschichten auf Aluminiumoxid-Substraten. Neben der Variation von Pulverfraktion und Substrattemperatur wurde ebenfalls untersucht, welchen Einfluss eine nachfolgende Warmebehandlung auf die Haftfestigkeit und Harte der Schichten hat. Mittels Rasterelektronenmikroskopie wurde die Splatmorphologie einzelner Spritzpartikel analysiert, wahrend ein hochauflosendes Transmissionselektronenmikroskop fur die Untersuchung des Al/Al2O3-Interfaces eingesetzt wurde. Erste Resultate lassen vermuten, dass mechanische Verklammerung der primare Haftmechanismus auf polykristallinen Substraten mit einer Oberflachenrauheit im Submikrometerbereich ist, wahrend fur Aluminiumschichten auf monokristallinen, atomar glatten Saphirsubstraten (α-Al2O3) heteroepitaktisches Wachstum als Hauptbindungsmechanismus wirkt. Die Heteroepitaxie wird dabei von verformungsinduzierten Rekristallisationsprozessen des kaltgasgespritzten Aluminiums begunstigt.

In Hybridlaminaten werden die positiven Eigenschaften metallischer und faserverstarkter polymerer Komponenten miteinander kombiniert. Vorteile der thermoplastischen Kunststoffkomponente, wie z. B. Umformbarkeit und Recyclingfahigkeit sowie Grosserientauglichkeit, bieten einen herausragenden Vorteil gegenuber duroplastischen Matrices. Zur Herstellung der Hybridlaminate werden in einem ersten Schritt Endlosfasern und Thermoplastfolien zu unidirektional faserverstarkten Tapes vorkonsolidiert. Anschliesend werden diese belastungsgerecht mit der metallischen Komponente verpresst, wobei das Interface zwischen faserverstarktem Thermoplast und der metallischen Folie eine entscheidende Rolle spielt. Im vorliegenden Beitrag werden Hybridlaminate mit kohlenstofffaserverstarktem Polyamid (CF-PA6) als Kernschichten und glasfaserverstarktem Polyamid (GF-PA6) als Zwischenschicht zur metallischen Komponente untersucht. Bei den Laminaten kommt ein 2/1- sowie 3/2-Aufbau mit zwei bzw. drei Metalllagen sowie einer bzw. zwei Lagen faserverstarkten Kunststoffes zum Einsatz. Als metallische Folie werden die Aluminiumlegierung EN AW-6082 und die Titanlegierung Ti3Al2,5V (Grade 9) verwendet. Die Laminatherstellung, die Entwicklung und die Einstellung des Interfaces sowie die Evaluierung der mechanischen Eigenschaften werden im Beitrag diskutiert. Hybrid laminates combine the positive properties of the metal and fibre reinforced plastic (FRP) components. Advantages of the FRP, like formability, recyclability as well as suitability for mass production, provide an outstanding advantage over thermosetting matrices. For the production of the hybrid laminates, at first continuous fibers and thermoplastic films are pre-consolidated to fibre-reinforced unidirectional tapes. Subsequently, these are pressed together with the metal component in a loadcapable optimized arrangement. Thereby the interface between the FRP and the metal foils is of crucial importance. This paper focuses on hybrid laminates with carbon-fiber reinforced polyamide (CF-PA6) functioning as core layers and glass-fiber reinforced polyamide (GF-PA6) as intermediate layers between the centre and metal component. Laminates in 2/1 and 3/2 structure with two respectively three metal layers and one respectively two FRP layers are examined. For the metal foil, the aluminium alloy EN AW-6082 and the titanium alloy Ti3Al2.5V (Grade 9) are used. The production of these laminates, development and adjustment of the interface and the evaluation of mechanical properties are investigated in this article.

Effizienter Leichtbau erfordert intelligente Werkstoffe, die vielseitige Funktionen erfullen. Ein Losungsansatz besteht darin, Kohlenstofffasergewebe galvanisch zu metallisieren, um funktionelle kohlenstofffaserverstarkte Kunststoffe (CFK) herzustellen. Es resultiert eine rissfreie, homogene Nickelschicht auf der Gewebeoberflache. Durch eine geeignete Wahl der Beschichtungsparameter wird daruber hinaus jede einzelne Faser des gesamten Gewebes gleichmasig metallisiert und eine Anwendung in funktionellen kohlenstofffaserverstarkten Kunststoffen fur Leichtbauwasserstoffspeicher ermoglicht. Schlusselworter: Metallisierte Kohlenstofffasern / funktionelle CFK / galvanische Abscheidung Efficient lightweight construction requires intelligent materials that meet versatile functions. One approach to produce functional carbon fiber-reinforced plastics (CFRPs) is the metallization of carbon fiber fabrics. This results in a crack-free, homogeneous nickel layer on the fabrics’surfaces. By selecting suitable layer parameters, every single fiber of the entire fabrics will be evenly metallized and allow the application of functional CFRPs as lightweight hydrogen storage.

Adhasions- und Versagensmechanismen an der Titan-PEEK-Grenzflache in Ti-CF/PEEK-Laminaten wurden im Mixed-Mode-Bending-Versuch bei uberlagerter Mode I- und Mode II-Belastung vor und nach hydrothermischer Alterung untersucht. Durch eine laserinduzierte kolumnare Oxidstruktur der Titanoberflache wird die Adhasion zwischen Titan und PEEK vor und nach Alterung erhoht. Die gute Adhasion entsteht durch Polymer, das herstellungsbedingt in die Zwischenraume der kolumnaren oxidischen Saulen eingedrungen ist und dort mikromechanisch verklammert. Das Polymer kann sich bei Belastung verstrecken (orientieren) und verfestigen. Die mikroskopischen Versagensmechanismen nach Alterung (Versagen im grenzflachennahen PEEK) bleiben im Wesentlichen unverandert. Die mikrostrukturierte Oberflache fuhrt zur deutlich verbesserten Langzeitstabilitat der Adhasion zwischen Titan und PEEK in feuchtwarmer Umgebung. Die makromechanische Adhasion von PEEK an die Titanoberflache entsteht durch PEEK, das herstellungsbedingt zwischen laserinduzierte Napfchenboden und -rander geflossen ist und dort verklammert. Der makroskopische Versagensmechanismus an der Grenzflache andert sich durch Alterung von makromechanischer Adhasion mit duktilem Versagen im PEEK zur teilweisen Abscherung der laserinduzierten Napfchenrander und Schmelzspritzer. The adhesion and failure mechanism at well-designed titanium-PEEK interfaces within Ti-CF/PEEK laminates are investigated by superposed mode I- and mode II-loading before and after hydrothermal aging. The laser-induced columnar structured oxide layer enhances the adhesion at the Titanium-PEEK interface. PEEK-Polymer that is locked mechanically in the capillary gaps of the columnar oxide structure are stretched and stiffed in the case of loading resulting in good adhesion. The adhesion at the oxide structure reduces by the influence of hydrothermal aging. Basically, the failure mechanism is not changed. Thus, the columnar oxide structure leads to enhanced humidity resistance of the adhesion between titanium and PEEK. The PEEK-Polymer is also locked in the undercuts between the depressions and rims of the laser-induced dot-like surface structure resulting in adhesion. The adhesion at the dot-like structured surface is nearly completely reduced by the influence of hydrothermal aging. The failure mechanism is changed from ductile failure within the PEEK-Polymer to party disrupted rims and melt spatter.

Warmedammschichtsysteme (WDS) bestehen in der Regel aus einer metallischen Haftschicht und einer keramischen Deckschicht. CoNiCrAlY-Superlegierungen finden als Haftschichtmaterial weit verbreiteten Einsatz, fur die Deckschichten wird oft Yttriumoxid-stabilisiertes Zirkondioxid verwendet. In der Folge der Langzeiteinwirkung von sauerstoffhaltigen Atmospharen bei hohen Temperaturen auf die Warmedammschichtsysteme kommt es zur Diffusion von Sauerstoff durch die porose Keramikschicht und zu Oxidationsprozessen an der inneren Grenzflache zur Haftschicht. Legierungskomponenten der Haftschicht bilden die so genannte thermisch gewachsene Oxidschicht. Das dabei auch entstehende α-Al2O3 behindert die Sauerstoff-Diffusion und verlangsamt so den Oxidationsprozess, was sich positiv auf die Einsatzdauer des Schichtsystems auswirkt. Die Verteilung der Legierungselemente in der Haftschicht bewirkt jedoch in der Regel die Bildung von gemischten Oxidphasen, wobei die Oxide unterschiedliche Wachstumsgeschwindigkeiten aufweisen, was zu lokalen Spannungen, Mikrorissen und Abplatzungen fuhrt. Dies beschrankt in hohem Mase die Lebensdauer von Warmedammschichtsystemen. In der vorliegenden Arbeit wird der Einfluss einer dunnen dampfabgeschiedenen Aluminium-Zwischenschicht auf die Eigenschaften eines thermisch gespritzten Warmedammschichtsystems untersucht. Die etwa 1 µm dicke Zwischenschicht wurde in einem zusatzlichen Prozessschritt zwischen Haft- und Deckschicht appliziert. Unter einsatznahen Auslagerungen in Atmospharenofen wurde erreicht, dass sich homogene α-Al2O3-reiche Oxidschichten bilden, die das Potenzial fur ein verlangsamtes bzw. kontrolliertes Wachstum der thermischen Oxidschicht besitzen. Erste Untersuchungsergebnisse zu Oberflachenbeschaffenheit, Mikrostruktur, chemischer Zusammensetzung und Spannungszustand vor und nach Temperaturwechselbelastungen werden fur die so modifizierten Warmedammschichtsysteme im Vergleich zu Standardsystemen dargestellt. Thermal barrier coatings (TBC) generally consist of a metallic bond coat (BC) and a ceramic top coat (TC). Co–Ni–Cr–Al–Y metallic super alloys and Yttria stabilised zirconia (YSZ) have been widely used as bond coat and top coat for thermal barrier coatings systems, respectively. As a result of long-term exposure of thermal barrier coatings systems to oxygen-containing atmospheres at high temperatures, a diffusion of oxygen through the porous ceramic layer occurs and consequently an oxidation zone is formed in the interface between ceramic top coat and metallic bond coat. Alloying components of the BC layer create a so-called thermally grown oxides layer (TGO). One included oxide type is α-Al2O3. α-Al2O3 lowers oxygen diffusion and thus slows down the oxidation process of the bond coat and consequently affects the service life of the coating system positively. The distribution of the alloying elements in the bond coat layer, however, generally causes the formation of mixed oxide phases. The different oxide phases have different growth rates, which cause local stresses, micro-cracking and, finally, delamination and failure of the ceramic top coat layer. In the present study, a thin Al inter-layer was deposited by DC-Magnetron Sputtering on top of the Co–Ni–Cr–Al–Y metallic bond coat, followed by thermal spraying of yttria-stabilised zirconia (YSZ) as a top coat layer. The deposited Al inter-layer is meant to transform under operating conditions into a closed layer with high share of α-Al2O3 that slows down the growth rate of the resulting thermally grown oxides layer. Surface morphology and microstructure characteristics as well as thermal cycling behaviour were investigated to study the effect of the intermediate Al layer on the oxidation of the bond coat compared to standard system. The system with Al inter-layer shows a smaller thermally grown oxides layer thickness compared to standard system after thermal cycling under same conditions.

Konventionelle Temperaturmessungen im Hochtemperaturbereich (>1400 °C) unterliegen starken Einschrankungen. Thermoelementschutzhullen fur Temperaturmessungen in Metallschmelzen sind mehrheitlich Einwegsysteme. Im Rahmen eines FuE-Projektes wird ein neuartiges Temperaturmesssystem entwickelt. Die Anforderungen an die Schutzhulle sind komplex. Sie muss sowohl temperaturbestandig, medienbestandig in Metallschmelzen, gasdicht, thermoschockbestandig, warmeleitfahig als auch bruchzah sein. Die zurzeit eingesetzten Werkstoffe fur die Schutzsysteme erfullen diese Anforderungen nicht. Einen neuen Ansatz stellt ein beschichteter C/(C/C–SiCN)-Hybridverbund dar, welcher aus Glaskohlenstoff sowie aus einem C/C–SiCN-Verbund besteht. Um die Medienbestandigkeit der Schutzhulle zu gewahrleisten, wird je nach Anwendungsfall eine entsprechende Beschichtung durch ein thermisches Spritzverfahren appliziert. Das Fugen des Tubus-Hybridverbundes mit dem gasdichten Verschluss des Tubusses bereitet auf Grund hoher Anforderungen, die an die Fugestelle gestellt werden Probleme. Die Fugeverbindung muss bei Temperaturen bis zu 700 °C ausreichend mechanisch stabil, und gasdicht sein. Bereits bewahrte Fugeverfahren fur Grafit sollen auf Glaskohlenstoff angewendet werden. Dazu wurde das Aktivhartloten untersucht. Im Beitrag werden konventionelle Aktivhartlote in Abhangigkeit des Titangehalts unter Variation der Prozessparameter hinsichtlich ihrer Eignung als Lotwerkstoff validiert. Die geloteten Proben wurden materialografisch, mikromechanisch und fraktografisch charakterisiert. Conventional high temperature (>1400 °C) measuring techniques are very limited. Thermal protective covering of temperature measuring elements in molten metals usually are single-use systems. As a part of a research and development project a new temperature measuring system is being developed. The requirements for this protective cover are extremely complex. Not only does it has to be resistant to high temperatures, media in molten metals, fractures and thermal shocks, it also has to be gastight and thermal conductive. The compounds used currently for these covers don't fit this profile. Laminated C/(C/C–SiCN) hybrid composites are a new approach, consisting of glassy carbon and a C/C–SiCN composite. In order to ensure the media resistance of the protective cover a fitting lamination is applied by means of a thermal spraying. Due to the extreme requirements of the joining points the joining of this lens barrel hybrid composite with the gastight seal is quite difficult. The joints have to maintain an adequate mechanical stability and gasthightness for up to 700 °C. Other reliable joining techniques for graphite are supposed to be applied to glassy carbon. Regarding this active hard soldering was investigated. In this article conventional active hard soldering agents with varying titanium contents and under variation of other parameters are tested for their suitability as a soldering agent. The soldered samples were material graphically, micromechanically and fractographically characterised.

Nanoparticles exhibit a decrease in sintering and melting temperature with decreasing particle size. The utilization of this effect is of great interest for joining at low temperatures. First, the paper identifies possible applications for joining and their significance. Furthermore, a commercially available Ag nanopaste is characterized with respect to its thermal properties and strength behavior. Subsequently, it is qualified for joining at low temperatures. The shape, distribution and size of the nanoparticles are determined using transmission electron microscopy (TEM). The thermal behavior is characterized by differential scanning calorimetry (DSC) and thermogravimetry (TG). Furthermore, first examinations of strength properties were executed for the base material copper in order to characterize the influence of different process parameters on joining strength. The analyses show that the nanopaste has a great potential for joining at low temperatures. It is verified that the organic shell of the nanoparticles oxidatively decomposes at temperatures of about 410 °C followed by a sintering process. The sintered microstructure exhibits the thermal properties of bulk silver. It is also shown, that it is possible to produce joints at even lower temperatures of about 300 °C, whose thermal resistance and joint strength is significantly superior to conventional soldered joints.

Powder-metallurgical Al–Cu alloy composites with Al2O3 and SiC particles have been anodised. The microstructure of the resulting oxide layers with respect to the composition of the matrix and the reinforcing particles has been correlated to nanoindentation results. The reinforcing particles are well-bonded in the conversion layer regardless of remaining stable (Al2O3) or being converted to mixed oxides (SiC → AlxSiyOz). The distinctive pore structure of the matrix conversion layer is known from anodising of bulk Al–Cu alloys and impedes the formation protective coatings on the studied composites. A shell of partly or completely converted aluminium on the Al–Cu composite shows options to improve the hardness of anodised aluminium oxide coatings on Al–Cu alloy composites.

The metallization of ceramics by means of cold gas spraying (CGS) has been in the focus of numerous publications in the recent past. However, the bonding mechanism of metallic coatings on non-ductile substrates is still not fully understood. Former investigations of titanium coatings deposited on corundum revealed that a combination of recrystallization induced by adiabatic shear processes and hetero-epitaxial growth might be responsible for the high adhesion strengths of coatings applied on smooth ceramic surfaces. In the present work, the interface formation between CGS aluminum and alumina substrates is examined for different particle sizes and substrate temperatures. Furthermore, the influence of subsequent heat treatment on tensile strength and hardness is investigated. The splat formation of single particles is examined by means of scanning electron microscopy, while a high resolution transmission electron microscope is used to study the Al/Al2O3 interface. First results suggest that mechanical interlocking is the primary adhesion mechanism on polycrystalline substrates having the roughness in sub-micrometer range, while the heteroepitaxy between Al and Al2O3 can be considered as the main bonding mechanism for single-crystalline sapphire (α-Al2O3) substrates with the surface roughness in nanometer range. The heteroepitaxial growth is facilitated by deformation-induced recrystallisation of CGS aluminum.

Aluminum phosphate was deposited onto bundles of carbon fibers and flat glassy carbon substrates using atomic layer deposition by exposing them to alternating pulses of trimethylaluminum and triethylphosphate vapors. Energy dispersive X-ray spectroscopy (EDXS) and solid state nuclear magnetic resonance (SS-NMR) spectra confirmed that the coating comprises aluminum phosphate (orthophosphate as well as other stoichiometries). Scanning electron microscopic (SEM) images revealed that the coatings are uniform and conformal. After coating, the fibers are still separated from each other like the uncoated fibers. Thermogravimetric analysis (TGA) indicates an improvement of oxidation resistance of the coated fibers compared to uncoated fibers.

Wire arc spraying is an economically attractive thermal spray process that is especially interesting for the protection of large-scale parts or constructions. This study presents the results of the development and investigation of a number of cored wires based on the Fe-Cr-Al system with minor addition of alloying elements (B, Mn, Ni, Si, Ti, Mg, etc.). The microstructure of the coatings, their electrochemical behavior, and isothermal oxidation performance over a temperature range of 20-700 °C were investigated. Erosion resistance at elevated temperatures was determined with a laboratory test unit under test conditions that have simulated the work conditions in fossil-fuel-fired boilers. It was established that the oxidation resistance and the gas-abrasive wear resistance of arc-sprayed coatings depend mostly on the coating microstructure and homogeneity of element distribution rather than on the general alloying level and microhardness of the coating. A new parameter for coating characterization, namely, the coefficient of chemical microheterogeneity, K CMH, is introduced to quantify this influence. Formation of the coating microstructure at elevated temperatures and its influence on the protection ability of the coating are discussed.

Recently a demand-driven development of iron-based coatings that could be an alternative for self-fluxing and cermet coatings for the protection of screen tubes of boilers of power stations has been observed. Electric arc spraying is an advantageous method in many applications due to its high deposition rate and economical operation (Crawmer, 2004) [1] . The fast development of cored wires as a feedstock material over the past few decades has made it possible to extend the metallurgical choice of sprayed coatings significantly. In the present work, the results concerning the development of arc-sprayed iron-based coatings for application at elevated temperatures are presented. Powder-cored wires have a diameter of 1.8 mm with a filling coefficient of 20–27%, a 0.4 mm thick cover, made of low-carbon steel (0.08% C), and contain a filling powder (Al, Cr, Mg, B). High resistance of coatings against hot-gas corrosion and erosion at elevated temperatures in oxidising atmosphere is ensured by the appropriate choice of an alloying system as well as the optimisation of deposition and, if needed, post-treatment processes. Oxidation kinetics, phase transformation and an evolution of the residual stresses in the coatings have been investigated at a temperature up to 700 °C for the time interval 100–2000 h. It has been established that the oxidation resistance of arc-sprayed coatings depends on the coating microstructure, phase transformation and oxidation processes, which take place during the high-temperature exposure, as well as on the level of chemical inhomogeneity of the arc-sprayed coating. The high resistance against gas abrasion is provided due to the favourable changes in the coating microstructure at the service temperature (600–700 °C) namely dispersing strengthening, desired oxidation sealing effect and formation of the beneficial compressed residual stresses.

International audience; The microstructure of ZrO2+8 wt.% Y2O3 coatings has been studied by means of transmission electron microscopy (TEM) including selected-area electron diffraction (SAED) and electron backscatter diffraction (EBSD). The coatings were suspension-plasma-sprayed onto stainless steel substrates. The parameters spray distance and torch scan speed had been varied. Both diffraction methods have confirmed the tetragonal lattice structure of the suspension-plasma-sprayed zirconia. The combination of TEM and EBSD allowed a detailed analysis of the size, shape and orientation of grains. The microstructure of the coatings is mainly lamellar, consisting of columnar grains. Additional microstructural features indicate that powder particles have been subjected to different modifications during spraying. The influence of the variation of spraying parameters on the microstructure is marginal.

Charging racks are used for the positioning and transport of workpieces in heat treatment and high-temperature brazing processes. Conventionally, they are made of steel or cast iron, but in recent years, more and more companies have changed over to charging racks made of light-weight materials such as graphite or carbon fiber-reinforced carbon (C/C). However, the main problem of these carbon-based workpiece carriers is the undesired carburization of components, which are in contact with the rack, by means of diffusion processes. For that reason, within the scope of the presented work, thermally sprayed coatings were applied on C/C and extensively tested for their suitability as high-temperature diffusion barrier. The ceramic powders Al 2 O 3 , Al 2 O 3 /Cr 2 O 3 , Al 2 O 3 /TiO 2 and ZrO 2 /Y 2 O 3 were chosen as coating materials and processed by powder flame spraying (PFS) and atmospheric plasma spraying (APS). Molybdenum and silicon carbide served as adhesion-promoting intermediate layers. Coating characterization included materialographic analyses, tensile strength and tribometric tests as well as long-term high-temperature tests, both laboratory-scaled and in industrial practice. Especially Al 2 O 3 and Al 2 O 3 /Cr 2 O 3 coatings on siliconized C/C exhibited excellent results, proving the wide application potential of thermally sprayed ceramic coatings on carbon-based light-weight materials.

Fibre Metal Laminates (FML) consisting of alternating stacked layers of polymer matrix composites and metallic foils are considered for structures with high fracture toughness and good impact resistance in aeronautic applications. The properties of thermoplastic Fibre Metal Laminates composed of titanium and carbon fibre reinforced polyetheretherketone (Ti/CF-PEEK laminates) are under investigation at DLR. The adhesion between the polyetheretherketone (PEEK) matrix and titanium degrades by the influence of humidity. Physical, chemo-physical and chemical surface pre-treatments of the titanium layers were tested to improve the long-term behaviour of the interface. To compare the different surface treatments, lap shear specimens were prepared and partly exposed to hot water (80 °C). Lap shear tests were conducted to determine the degradation of the initial strength by the influence of water. Concerning the physical pre-treatment, the laser pre-treatment offers the highest magnitude of humidity resistance because of the magnitude and kind of surface roughness. Concerning the chemo-physical pre-treatment, the anodization offers reduced initial bonding strength and reduced humidity resistance caused by the created oxide layer. Concerning the chemical pre-treatment, the usage of adhesion promoter causes enhanced initial bonding strength but also reduced humidity resistance.

Carbon fibres are fabricated in bundles. A single roving contains a minimum of 1000 filaments. Certain applications demand thinner bundles or even single fibres. Single fibres can be used as tool electrodes in electrochemical machining processes. Thinner rovings are needed in sensor applications to raise the electrical resistance of the carbon fibre bundle used as strain sensor. Rovings with a lower filament count cannot be delivered by carbon fibre producers. A splitting technology is therefore needed. A continuous bundle splitting technique was developed. It uses mechanical means, liquid flow and variations in winding force and speed to separate the filaments. The impact of winding parameters and of the liquid flow on the splitting result was quantified in experiments with the developed splitting system. An automatic and continuous splitting of carbon fibre rovings was realised. Smaller bundles of carbon fibre filaments can be provided. There is a solution to satisfy the demand on finer carbon fibre rovings.

The processing of polymers necessitates the use of corrosion and wear resistant tool materials being in direct contact with the feedstock material. Corrosion resistant cold work tool steels, the so called plastic mold steels, are successfully applied here, offering both a good wear and corrosion resistance. The lifetime of this tool depends on the applied heat treatment but also the processing route has a distinct effect on the resulting properties. In this work, different powder metallurgical routes like hot isostatic pressing, build-up welding (plasma transfer arc (PTA)) and thermal spraying (high velocity oxy fuel (HVOF) and atmospheric plasma spraying (APS)) were applied to produce coatings on low-alloyed construction steel. Coatings are compared in relation to the changes in microstructure and the feasibility of an adequate heat treatment. This paper discusses strategies to maximize wear resistance in dependence of heat treatment and the microstructural changes arising from the processing. Die Verarbeitung von Polymeren erfordert den Einsatz von korrosions- und verschleisbestandigen Werkzeugstahlen. Korrosionsbestandige Kaltarbeitsstahle, die sogenannten Kunststoffformenstahle, werden in diesem Bereich erfolgreich eingesetzt, da diese sowohl eine gute Korrosions-, als auch eine gute Verschleisbestandigkeit bieten. Die Standzeit dieser Stahle hangt zum einen von der durchgefuhrten Warmebehandlung ab. Zum anderen ubt aber auch der Herstellungsprozess einen masgeblichen Einfluss auf die resultierenden Eigenschaften aus. In dieser Arbeit wurden die pulvermetallurgischen Fertigungsrouten Heis-Isostatisches-Pressen, PPA-Schweisen und das thermische Spritzen (HVOF, APS) verwendet, um eine Beschichtung auf einem niedrig legierten Baustahl zu erzeugen. Die Beschichtungen wurden dabei in Hinblick auf die Anderungen der Mikrostruktur durch die Herstellung sowie der Warmebehandlung untersucht. Das Ziel dieser Arbeit ist es, eine Steigerung der Verschleisbestandigkeit in Abhangigkeit der durchgefuhrten Warmebehandlung und des Herstellungsprozesses zu erzielen.

Es wird auf die Notwendigkeit der FE-Simulation und die dabei anfallenden Arbeitsschritte bei der Optimierung von beschichteten Umformwerkzeugen eingegangen. Nach der auf die konkrete Anwendung abgestimmten Schichtauswahl werden Materialparameter bestimmt und die dabei auftretenden Probleme bei Dunnschichten (Dicke in der Grosenordnung von 2 μm) werden diskutiert. Die speziellen Probleme bei der numerischen Losung der Modelle werden ebenfalls angesprochen. Letztendlich werden Ergebnisse der Simulation erlautert und Modifikationen in Variantenrechnungen untersucht. The need for FE-simulation and the occurring work packages during optimization of coated forming tools are described. After the coating material selection concerning the concrete application material parameters are identified. The occurring problems due to the small thickness (thickness in the order of 2 μm) are discussed. Also the particular numerical problems during the solution of the numerical models are mentioned. Finally simulation results are shown and modifications in variant simulations are analyzed.

Fur das Fugen der Aluminiumlegierung EN AW-6012 und des Aluminiummatrix-Verbundwerkstoffes EN AW-2017 + 10 Vol.-% (Al2O3)P mittels des Zinkbasislotes ZnAl4 wird das ultraschallunterstutzte Widerstandsloten angewendet. Untersucht werden die Einflussgrosen Anpresskraft, Transformator- und Ultraschallleistung sowie die Auswirkung unterschiedlicher Fugeflachengeometrien auf die Verbindungseigenschaften. Als wesentlicher Indikator dient dabei die Verbindungsfestigkeit, welche im 3-Punkt-Biegeversuch ermittelt wird.

Ein geeignetes Verfahren zur Herstellung partikelverstarkter Aluminiumwerkstoffe ist das Hochenergie-Kugelmahlen (HEM) mit anschliesender Kompaktierung. Der Schritt HEM hat dabei die Aufgabe harte Partikel in duktilem metallischem Pulver moglichst homogen zu verteilen. Eine andere Anwendung von HEM ist das mechanische Legieren. Der vorliegende Beitrag beschaftigt sich mit der Kombination beider Effekte. Rein metallische Pulver (Al, Cu, Mg, Mn) wurden dazu gemeinsam mit SiC-Pulver als Verstarkungskomponente bis zu 10 h gemahlen. Die Zusammensetzung der metallischen Pulver entspricht der der Legierung EN AW-2017 (3,9% Cu, 0,7% Mg, 0,6% Mn). In bisherigen Versuchen wurde diese Legierung in Form von verdustem Pulver verwendet. Die mikrostrukturellen Vorgange innerhalb der sich bildenden Pulverteilchen wahrend des Mahlens werden ausfuhrlich mittels Lichtmikroskopie, REM, EDXS und XRD untersucht. Die Ergebnisse zeigen, dass die Herstellung von Verbundpulver in nur einem Schritt moglich ist. Dies erlaubt nicht nur die wirtschaftlichere Herstellung derartiger Pulver, sondern ermoglicht auch die Verwendung von Legierungszusammensetzungen, welche nicht oder nur schwer schmelzmetallurgisch herstellbar sind. Die Herstellung von tailor-made-Legierungen bietet sich an. High-energy ball milling (HEM) with subsequent consolidation is a suitable method to produce particle-reinforced aluminium materials. The task of HEM is to distribute the reinforcement particles as homogeneously as possible. A further application of HEM is mechanical alloying (MA). This paper deals with the combination of both applications. Pure metallic powders (Al, Cu, Mg, Mn) were milled together with SiC particles up to 10 h. The composition of the metallic powder corresponds to that of the alloy AA2017 (3.9% Cu, 0.7% Mg, 0.6% Mn). In previous experiments [1], this alloy was used in the form of atomized powder. The changes in microstructure during the formation of the composite powder have been studied by light microscopy, SEM, EDXS and XRD. The results show that the production of composite powders in a single step is possible. This not only allows the economical production of such powders, but also facilitates the use of alloy compositions that are not producible via the melting route, or only producible with difficulty via the melting route. It's possible to produce tailor-made-alloys.

This article deals with powder metallurgical production and modification of properties of a composite material based on an age-hardenable Al–Cu alloy. The main objective is to improve the mechanical properties by particle reinforcement and equal-channel angular pressing (ECAP). Our approach makes use of four hardening mechanisms: precipitation hardening, particle reinforcement, strain-hardening, and grain boundary hardening associated with an ultrafine-grained microstructure produced by ECAP. The main processing steps are high-energy ball milling, hot-isostatic pressing, extrusion, heat treatment, and a single ECAP pass. Microstructures are analyzed by optical microscopy, scanning electron microscopy, and scanning transmission electron microscopy. The mechanical properties are characterized by hardness measurements and quasi-static tensile testing. Our experimental results show that the proposed processing route results in a nearly homogeneous distribution of SiC particles in the matrix. The combination of particle reinforcement and ECAP leads to an improvement of ultimate tensile strength by almost 300 MPa compared to the unreinforced alloy. A subsequent heat treatment leads to a further increase in hardness and strength that can be related to changes in the defect structure. Our study provides detailed information on how processing steps, microstructures, and mechanical behavior are interrelated in this technologically relevant class of materials.

High-strength materials on the basis of aluminum are attractive candidates for use in applications such as safety components that require high strength, high quality and integrity of various properties. In this paper, we discuss recent improvements in terms of property optimization made in the fields of (1) ultrafine-grained aluminum alloys prepared by equal-channel angular pressing, and (2) aluminum matrix composites with particle reinforcement. We discuss microstructural aspects and mechanical properties, as well as technological (processing parameters), wear and corrosion behavior. Our results highlight recent — and potential for further — improvements and for future applications of high-strength, aluminum-based materials.

Electron backscatter diffraction is used to study the microstructural evolution of cold-spray aluminum coatings on Al2O3 substrates. The influence of powder purity and substrate heating on the kernel average misorientation and the distribution of low-angle grain boundaries in as-sprayed and annealed coatings are discussed in terms of dynamic recovery and dynamic recrystallization.

Catalytic incineration of toluene over γ-Al2O3-supported copper–manganese oxide catalysts in the temperature range of 433 K–553 K was investigated using a fixed-bed flow reactor. Catalysts were characterized using Brunauer-Emmett-Teller surface area analysis, scanning electron microscopy, temperature-programmed reduction, temperature-programmed oxidation, X-ray photoelectron spectroscopy, and X-ray diffraction. Incineration of toluene was achieved at temperatures up to 553 K and it was found that the weight ratio of reactants (Cu:Mn) was optimized to be 15:10. Brunauer-Emmett-Teller surface area results had no correlation with the activity of the catalysts. Results of temperature-programmed reduction/temperature-programmed oxidation and X-ray photoelectron spectroscopy showed that the redox peak of the 15Cu-10Mn catalyst shifted at lower temperatures and the binding energy shifted toward higher oxidation levels. These results show that high binding energy and high redox capacity are the causes of...

There has been an increased demand for lightweight composite materials in recent years. In particular, aluminium-matrix composites (AMC) have been applied in many different sectors such as the aerospace industry, automobile production, or power-electronics. Composite filler metals with low melting ranges and adjusted technologies have been especially developed for joining temperature-sensitive AMCs. These special composites produced by equal-channel angular pressing feature a very high strength due to a very fine-grained structure. As a result of the addition of ceramic reinforcement components, an improvement of mechanical properties of the fillers has been achieved. In the present investigations, the microstructure of the joints and the influence of thermal treatment during the joining process on the temperature-sensitive base material were demonstrated. Therefore, the Brinell hardness was measured. The results show a high joining strength due to the use of the composite fillers but also a deterioration in the properties of the base material.

Das Fugen von temperaturempfindlichen Aluminiummatrix-Verbundwerkstoffen erfordert geeignete Lotwerkstoffe und angepasste Fugetechnologien. Dabei existieren unterschiedliche Losungsansatze. Einerseits zeichnen sich die entwickelten, partikelverstarkten Zinnbasislote durch niedrige Verarbeitungstemperaturen und gesteigerte mechanische Eigenschaften aus. Andererseits ermoglichen die entwickelten, ultraschallunterstutzten Lottechnologien mit induktiver bzw. widerstandsbasierter Erwarmung den Einsatz von Zinkbasisloten. Die notwendige Lottemperatur wird dabei lokal in der Fugezone erzeugt. Die Kombination mit der Ultraschalleinleitung stellt eine flussmittelfreie Benetzung der Fugeflachen sicher. The joining of temperature-sensitive aluminium matrix composites requires appropriate fillers and adapted joining technologies. Thereby different solutions are possible. On the one hand, the developed, particulate-reinforced tin based fillers are featured by a low process temperature and increased mechanical properties. On the other hand, the developed, ultrasound supported soldering technologies (inductive respectively resistance based heating) allow the use of zinc based fillers. The required heat input is realised locally. In combination with an ultrasound process a fluxless wetting is obtained.

Ein geeignetes Verfahren zur Herstellung partikelverstarkter Aluminiumwerkstoffe ist das Hochenergie-Kugelmahlen (HEM) mit anschliesender Kompaktierung. Bei dem Mahlverfahren haben neben anderen Parametern gegebenenfalls eingesetzte Trennmittel (PCA – process control agent) sowie die Atmosphare entscheidenden Einfluss auf die sich ausbildende Verbundpulverstruktur. Nach zahlreichen Forschungsbeitragen auf dem Gebiet der partikelverstarkten Aluminium-Werkstoffe der Autoren beschaftigt sich der vorliegende Beitrag mit der Evaluation verschiedener PCAs und mit dem Einfluss der unterschiedlichen Mahlatmospharen (Luft, Argon, Stickstoff) auf das Hochenergiekugelmahlen bei der Herstellung eines Verbundpulvers einer Aluminiumlegierung der 2xxxer Serie mit SiC-Partikeln. Die Untersuchungen zeigen, dass die Reaktion des Mahlgutes mit Luft die Mahleigenschaften des Aluminiumpulvers deutlich verandern. Die Verwendung eines PCAs ist dadurch, anders als bei inerten Atmospharen, nicht mehr notig. Fur das Mahlen mit PCA wird Menthol als Alternative zur Stearinsaure aufgezeigt. High-energy ball milling (HEM) with subsequent consolidation is a suitable method to create particle-reinforced aluminium materials. In addition to other parameters, the used PCA (process control agent) as well as the atmosphere significantly influence the milling procedure. After numerous scientific contributions in the field of aluminium matrix composites by the authors, the present paper deals with the evaluation of several PCAs and the influence of different milling atmospheres (air, argon, nitrogen) on high-energy ball milling for the creation of a composite powder of an aluminium alloy of the 2xxxx series with SiC particles. The investigations show that the reaction of the mill material with air changes the milling properties of aluminium powder explicitly. Therefore, using PCAs is not necessary anymore unlike with inert atmospheres. For milling with PCA, menthol is shown as an alternative to stearic acid.

Im Sonderforschungsbereich 692 werden hochfeste Aluminiumlegierungen entwickelt, um den steigenden Anforderungen des Leichtbaus gerecht zu werden. Diese neuartigen Legierungen fuhren bei Umformwerkzeugen zu hohem Adhasionsverschleis. Aus Umweltschutzgrunden soll diesem nicht wie bislang durch verstarkten Trenn- und Schmiermitteleinsatz, sondern durch eine angepasste Werkzeugbeschichtung und/oder Modifikation der Randschicht begegnet werden. Zur Auslegung der Werkzeuge, Beschichtungen und Substrate, im besonderen Hinblick auf die erhohten thermomechanischen Belastungen, werden im Teilprojekt B1 Experimente in Kombination mit der Methode der Finiten Elemente (FEM) angewendet. Um die Schicht-Substrat-Systeme vollstandig numerisch abzubilden, werden Modelle und Materialparameter generiert. Im Besonderen wird dabei ein Schwerpunkt auf die schadigungsmechanische Simulation gelegt. Der Beitrag beschreibt die Oberflachencharakterisierung und Bestimmung allgemeiner mechanischer Parameter fur Dunnschichten und fokussiert auf die Erstellung von Schadensmodellen und Ermittlung von Schadensparametern. In the Collaborative Research Centre 692, high-strength aluminum alloys are being developed to meet the increasing demands in lightweight construction. These new alloys lead to high adhesive wear on forming tools. For environmental reasons, this is no longer to be eliminated by intensive application of lubricants but by adapted tool coating and/or modification of the surface. Within the subproject B1, the method of finite element (FEM) in combination with adequate is used for the design of the tools, coatings and substrates, with special regard to the higher thermo-mechanical loads. Numerical models for comprehensive simulation have been developed and material parameters analyzed. The considerations are particularly focused on the simulation of failure-mechanical incidents. This article describes the surface characterization and the determination of general mechanical parameters for thin coatings with special emphasis on the development of failure models and the determination of failure parameters.

Alumina coatings are widely used in a range of industrial applications to improve corrosion protection, wear and erosion resistances, and thermal insulation of metallic surfaces. Refined alumina surfaces with long-term use are obtained from various efficient and adjustable processes. It can be seen that costefficient arc-sprayed Al coatings post-treated by plasma-electrolytic oxidation (PEO) form Al2O3 -layers with remarkable corrosion protection, hardness, bonding strength, and abrasion resistance, as well as with the extended service time. The properties of these coatings are compared with alumina coatings obtained by flame spraying and atmospheric plasma spraying.

In the field of thermal spraying, cermets are known to have excellent wear-protecting properties. However, the high price of the spraying materials and the environmental aspects of nickel and cobalt utilization are often the limitations to their wider application. Within the frame of a multi-institutional cooperation of various German research centres, the AiF/DFG research cluster “Thermal Spraying” was organised, one of the main research goals of which is the development of economically attractive alternative spray materials with new property profiles. This paper presents some results of the project that deals with the development and thermal spraying of particle-reinforced iron-based composite alloys. High-alloyed steels serve as matrix materials into which hard CrB2 particles are incorporated by means of a high-energy milling (HEM) process. The microstructure of the powder and the level of its amorphisation can be strongly influenced by appropriate milling parameters that allow the adjustment of the desired nanocrystalline structure. By using the high-velocity oxygen fuel thermal spraying process (HVOF), the microstructure of the particles can be transferred to the coatings. The deposited coatings exhibit low porosity and high microhardness values of more than 1000 HV0.3. The high abrasion wear resistance of newly developed coatings evaluated by means of the Miller test (ASTM G75-01) makes them promising for application for example in paper industry as an alternative to hard chromium coatings.

Bundles of carbon fibers were successfully coated with alumina by atomic layer deposition via sequential exposures to trimethylaluminum and water at 77°C. Fibers were not damaged by this procedure. Scanning electron microscopy (SEM) images revealed that individual filaments were coated separately with a smooth layer; no bridging of fibers was observed. Transmission electron microscopy (TEM) and SEM images indicate that the coating was conformal and adhered well to the fiber surface. The average deposition rate was 0.25±0.02 nm/cycle, calculated from SEM images obtained at various positions of the fibers and of fibers coated with various numbers of cycles. In addition to image analysis, the coating thickness was as well estimated from the elemental composition of selected parts of a fiber bundle that was coated by 450 cycles. Along the fiber axis, the weight fraction of aluminum of the coated fibers varied from 5.3 to 6.5 wt% and perpendicular to the bundle axis it varied from 4.8 to 7.4 wt%. This translates into a variation of the estimated coating thickness along the fiber from 166 to 126 nm and perpendicular to it from 114 to 183 nm. One can estimate independently an average coating thickness from the analysis of SEM images of this specific bundle of 126 nm. The alumina coating improved oxidation resistance of the carbon fiber significantly. The oxidation onset temperature was 600°C for fibers coated with a 30-nm-thick layer of alumina and increased gradually with increasing coating thickness up to 660°C at a thickness of 120 nm. On the other hand, uncoated fibers started to oxidize already at 300°C.

Ceramic substrates for power electronic circuits or integrated components are usually metallised by cost-intensive thermal processes. Simple, flexible and cost-effective solutions are increasingly demanded for integrated power electronic devices. Cold gas spraying (CGS) can deliver these demands. It is employed to produce dense, well adherent and oxide free coatings with properties comparable to the respective bulk material. The CGS-metallisation of non-conductive parts for power electronic devices permits a direct assembly and contacting of semi-conductors. Industrially available Al2O3 substrates are first CGS-coated with aluminium, which acts as an adhesive layer. In a second step, the aluminium layer is coated with copper, which exhibits good electric properties. The conductive structure on the ceramic is achieved by using a laser cut steel template, which allows for a minimal circuit width of about 250 μm. In order to clarify the adhesion mechanisms of cold-gas sprayed aluminium on alumina coated samples were subjected to micro-structural characterisation with scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and electron backscatter diffraction (EBSD).

Im Leichtbau werden zunehmend massiv umgeformte Bauteile aus hochfestem Aluminium angewendet. Aufgrund okonomischer und okologischer Aspekte bei der Umformung ist ein Einsatz von wenig bzw. keinen Schmiermitteln und eine Modifizierung der Werkzeugoberflachen notwendig. Die richtige Auswahl des Beschichtungswerkstoffs ist entscheidend fur das Reibverhalten im Kontakt mit hochfesten Aluminiumwerkstoffen und somit ausschlaggebend fur die Standzeitverbesserung von Umformwerkzeugen. Zur Untersuchung des tribologischen Verhaltens von verschiedenen Beschichtungskonzepten wurden Proben mittels PVD- (Physical Vapour Deposition) und CVD-Verfahren (Chemical Vapour Deposition) mit verschiedenen Schichtsystemen beschichtet, charakterisiert und mit dem unbeschichteten Substrat 1.3343 (HS6-5-3) verglichen. Die Charakterisierung des tribologischen Verhaltens erfolgte durch Scratch- und Stift-Scheibe-Tests gegen eine Auswahl hochfester Aluminiumwerkstoffe mit und ohne Schmierstoffeinsatz. Zur Oberflachencharakterisierung diente das Tastschnittverfahren. Bei Verwendung von Schmierstoff verbessern die Beschichtungen das Reibverhalten im Vergleich zum Substrat nur unwesentlich. Dagegen reduzieren die DLC-basierten Schichtsysteme unter trockenen Bedingungen den Reibwert um bis zu 74% gegenuber Stahl. Den geringsten Reibkoeffizient gegen die drei ausgewahlten Aluminiumwerkstoffe unter trockenen Bedingungen besitzt das Schichtsystem “Plasmanitrieren + DLC”. The use of high-strength aluminium alloys for massive forming parts plays an increasing role in lightweight construction. The usage of less/without lubricant during massive forming and tool surface modification operations are significantly important because of the economical and ecological aspects. Selection of the high wear resistance material, which is in contact with high-strenght aluminum alloys, is curial for improving the service life of the forming tools. In this study, coatings were deposited on steel substrate 1.3343 (HS6-5-3) by PVD (Physical Vapour Deposition) and CVD (Chemical vapor deposition) techniques. The frictional behaviour of coating systems was characterized by a pin-on-disk tribometer with and without lubricant conditions. Surface profilometry was used to compare the surface topography of the coatings. The coating systems doesn't show remarkably tribological improvement in comparison to the steel 1.3343 under lubricant conditions. Wear test results showed that the DLC-based coatings reduce the friction coefficient by up to 74% compared to steel under dry conditions. It has been found that the best performance of tribological system without lubricant improved with the type of plasma nitriding + DLC coating system.