High‐performance Cu/Al laminated composites fabricated by horizontal twin‐roll casting

Horizontal twin‐roll casting technology was successfully introduced to produce high‐performance copper/aluminum (Cu/Al) laminated composites. The interface morphology, electrical properties and peeling strength after different annealing and cold rolling processes were investigated and contrasted with Cu/Al clad plates fabricated by conventional methods. The results show that sound metallurgical bonding between the copper and aluminum matrix can be attained after the horizontal twin‐roll casting processes and Al₂Cu is the only intermetallics at the interfacial region, the thickness of interfacial interlayer is about 0.7 μm. The peeling strength is 31.4 N/mm and can be further increased to 37.1 N/mm after annealing at 250 °C. However, higher temperature like 400 °C will cause the excessive growth of intermetallics so that peeling strength sharply decreases to 9.2 N/mm. Electrical conductivity of the clad plate is 51 MS/m. At the same electrical current intensity, the temperature‐rise of the composite plate is between the pure copper plate and the aluminum plate, and closer to the copper plate. All of the properties are outstanding than that of Cu/Al clad plate fabricated by conventional methods.     

Methoden zur mechanischen Charakterisierung von modifizierten Implantatoberflächen in der Orthopädischen Chirurgie

Methods for the mechanical characterisation of modified implant surfaces in orthopaedic surgery Nowadays, on average approximately 10 % of all hip and knee endoprostheses have to be exchanged within the first 10 years. Implant revision is often necessary following aseptic or septic loosening. Hence, today implants for orthopaedic surgery are increasingly being coated for better osseointegration. Coatings have to be biocompatible and meet high mechanical requirements, whereby the adhesive strength and the abrasive wear resistance of the coatings take on a key role. This study presents different methods to asses these parameters experimentally using two innovative coatings (TiN, TiO2‐Cu) exemplary. The adhesive bonding strength of the coatings was investigated using different standardised methods, such as the arbour bending test, scratch test and the standard adhesive test. Wear resistance was determined after 1.5 million cycles in a special testing machine. The investigations showed for both coatings, TiN and TiO2‐Cu, good adhesive strength and wear resistance. The adhesive strength and wear resistance of bio‐active, wear reducing or anti‐allergenic surface coatings can be determined reliably using the above‐mentioned methods.     

Hybrides Walzen am Beispiel von Titan‐Aluminium‐Verbunden

Hybrid rolling as exemplified by titanium‐aluminium laminates Triple layered titanium‐aluminium laminates composed of titanium alloys TiAl6V4 (ASTM grade 5) and Ti 99.8 ASTM grade 1) together with the aluminium alloys AlMgSi 0.5 (EN‐AW 6060) and AlCuMg 1 (EN‐AW 2017) are manufactured by hot rolling and the deformation behaviour is investigated subject to alternating deformation parameters. The focus is the investigation of the differences between stepwise and continuous increases in true strain. True strains of 20 … 60 % are tested at temperatures from 400 … 500 °C. The contact zone of the manufactured laminates is then metallographically examined and the interlayer bond strength is mechanically tested. Torsion tests are presented for qualitatively determining the bond strength of the laminate. Bond forming already initiates at true strains of 35 % and temperatures of 350 °C within the rolling gap.     

Verschleißfeste Beschichtungen von Aluminium‐Stahl‐Hybridstrukturen mittels thermischer Spritztechnik

Spraying of wear‐resistant coatings of aluminium‐steel‐hybrid‐structures By means of high velocity oxy fuel flame spraying of aluminium‐hybrid‐structures consisting of a Al Zn 5,5 Mg Cu 1,5 (ENAW7075) and a NiCrBSi‐coating as well as a Cr₃C₂ 25NiCr‐ coating are manufactured. The hybrid composite structures are analysed and compared with each other regarding to hardness, surface roughness, wear‐resistance and coating density.     

Enhancement of coating characteristics via improved plasma electrolytic oxidation set-up

The plasma electrolytic oxidation process involves high-temperature operations and exposed to corrosive chemicals. Thus it requires stringent experimental set-up to produce uniform and high-quality coatings. This study proposes an enhancement to the current plasma electrolytic oxidation experimental set up to improve: 1) electrode holder; 2) cathode-anode electrodes, and 3) water-cooling system. In this paper, the focus is dedicated to the first two items. For the first item, the redesigned electrode holder is developed using 3-dimensional software. For the second item, results due to cathode via stainless container as well as carbon electrode are discussed. The performance of the new set-up plasma electrolytic oxidation is compared with the old one by analysing the microstructure and the mechanical properties of titanium dioxide coatings formed on a titanium aluminium vanadium alloy substrate using both set-ups. Surface morphology shows that the coating produced using the new set-up is thicker, denser and has lower porosity as compared to the coating deposited using the old set-up. The mechanical properties of hardness and adhesive strengths of the coating are also improved in the new set-up. Thus, the use of this set-up is recommended for improved coating performance to produce a uniform coating having enhanced mechanical performance.     

Evaluation of the bonding behaviour of thin bio‐based wooden laminates

Thermoplastic laminates usually consist of oriented fibres in thermoplastic matrices. Commonly glass fibres or carbon fibres are used as reinforcement for such laminates. The application of thin wooden sheets (veneers) as reinforcement applications is new. Therefore the bonding of such combinations has to be investigated. Various tests can be used for evaluating the bonding between the components of the laminates. The aim of this study is to determine a fast and easy method suitable for quality control of new bio‐based wooden laminates.     

Effect of the surface treatment in polyurethane and natural leather for the footwear industry

This aim of this paper is to analyse the peel strength of an adhesive joint with various types of surface treatments in order to contribute to the research and development of adhesives for the footwear industry. In the shoe industry, the adhesive properties are very important to ensure the quality of manufacture of the shoe. To better understand the behaviour of the adhesive joint, it is important to measure the peel resistance of the adhesive and use it to adjust the manufacturing process. For this work, joints were manufactured using natural leather, polyurethane (PU) and a solvent based polyurethane non structural adhesive. The influences of the application of physical surface treatments and/or primer on substrates in the peel strength of a T joint were analyzed. Several tests were used to characterize the surfaces of the substrates, including Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM) and contact angle measurements. It was found that certain surface treatments are required to obtain an adhesive joint capable of satisfying the minimum requirements of the shoes manufacturing sector.     

Numerische und experimentelle Untersuchungen zur Herstellung von stranggepressten Aluminium/Magnesium‐Werkstoffverbunden und zur Festigkeit des Interface

Numerical and experimental investigations of the production processes of coextruded aluminium/magnesium‐compounds and the strength of the interface In the research project SFB 692 the aim of the subproject B3 is to analyze aluminium/magnesium‐compounds, especially the strength and fracture mechanical properties. Furthermore a numerical model of the interface should be created. In the following paper the main results of the investigations of the subproject are presented. Different influencing variables were analyzed, which determine the quality of the interface. It has been shown, that the compound quality and also the strength of the interface is based on several parameters of hydrostatic and indirect extrusion processes. If the quality of the interface is good, without cracks, the strength is very high. Furthermore the behaviour of the interface under loading in an extended temperature range is presented. A numerical model was found to visualize the behaviour of the compound during the loading tests.