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In water based solutions, electrodeposition of Pd and Pd alloys is complicated due to hydrogen embrittlement. This can be avoided by using non-aqueous solutions like deep eutectic solvents ...

Quenching and partitioning (Q&P) treatments result in promising mechanical properties of advanced high-strength steels. However, recent studies indicate that Q&P steels are very susceptible to hydrogen embrittlement (HE). Using slow strain-rate tests, the effects of hydrogen charging in different media without and with recombination poison were investigated for Fe-0.38C-1.92Si-0.66Mn-1.39Cr in quenched and tempered as well as Q&P conditions. In addition, corrosion tests and Zn electroplating of tensile specimens were performed. In both heat-treatment states, it was found that the intensified hydrogen-charging conditions using a recombination poison strongly impact the result of HE investigations: HE only occurs when a recombination poison is present. In addition, the negative influence of hydrogen formed during Zn electroplating can be limited by using proper electrolytes and electrical parameters. This allows keeping the HE susceptibility of the Q&P steel low in practical applications when recombination poisons are absent.

According to the concept of an intrinsic hybrid composite, adhesive bonding is designed for generating the connection between the applied fiber reinforced polymer and a metallic insert. To induce adhesive bonding, a metallic insert, made of aluminum, is coated. This contribution focusses on the development of a suitable coating system. To this end, the coating system must meet certain requirements. On one hand, demands on the coating like ductility can be deduced from analyzing the manufacturing process. On the other hand, requirements like corrosion protection as well as high static and dynamic strength arise from specific applications under considerations. The utilized coating system is based on organically modified silicate layers (Ormosil) applied using a sol–gel process. To prove that this coating system fulfils the requirements, the corrosion protection is analysed by impedance spectroscopy. Furthermore, different mechanical experimental investigations are performed to verify the ductility of the coating as well as the strength of the resulting interface. Hence, it is shown that the considered coating system can be applied for the analysed intrinsic hybrid composite manufactured in series.

Due to a combination of different classes of materials, intrinsic hybrid composites are characterised by high strength and low weight. The mechanical properties of hybrid parts are mainly determined by the interface between the different materials. Consequently, this interface has to be considered in detail within the development of an intrinsic hybrid composite. The general approach of the considered composite is the combination of a mechanical form fit with adhesive bonding. This contribution focuses on the development, production and characterisation of the interface between aluminium and a fibre reinforced polymer as well as of the hybrid composite.

In this study, the electrodeposition of palladium alloys was investigated in a choline chloride/urea based deep eutectic solvent containing sulfosalicylic acid dihydrate as organic additive and Pd(II) + Ag(I), Pd(II) + Pt (II), or Pd(II) + Pt (II) + Ag(I) as metal components. The electrochemical behavior of the electrolytes was characterised by cyclic voltammetry. The electrodeposition processes require nucleation overpotential. Energy-dispersive X-ray data indicated that the layer thickness and composition of the produced Pd–Ag, Pd–Pt, and Pd–Pt–Ag films could be varied by changing the deposition mode. Additions of Ag(I) to the Pd and Pd–Pt electrolytes enhanced the overall metal deposition rate. Scanning electron micrographs of the electrodeposits showed that in general, the Pd alloys deposited by pulse current were nodular and relatively compact, whereas the films deposited by potentiostatic deposition were less dense and covered with dendrite-like and sharp-edged crystallites. Data collected from X-ray diffraction (XRD) experiments proved the existence of metallic alloys.

Plasma electrolytic oxidation (PEO) is a common means for the surface modification of light metals. However, PEO of magnesium substrates in dilute electrolytes generally leads to the formation of coatings consisting of unfavorable MgO magnesium oxide. By incorporation of electrolyte components, the phase constitution of the oxide coatings can be modified. Coatings consisting exclusively of MgAl2O4 magnesium-aluminum spinel are produced by PEO in an electrolyte containing hydroxide, aluminate, and phosphate anions. The hardness of the coatings is 3.5 GPa on Martens scale on average. Compared to the bare substrate, the coatings reduce the corrosion current density in dilute sodium chloride solution by approx. one order of magnitude and slightly shift the corrosion potential toward more noble values.

In recent years, the growing environmental awareness has led to the development of energy-efficient products, for example by the replacement of steel as construction material by aluminium to save weight and thus increase the energy-efficiency of mobile systems. However, to address the energy-efficiency of a product holistically, the energy consumption of the production process also has to be considered. For the anodic oxidation process of the AlMgSi1 aluminium alloy, the influence of the sulphuric acid concentration, the glycolic acid concentration, the electrolyte temperature and current density on coating thickness, hardness, ductility and wear resistance (scratch test), as well as on the consumption of electrical energy and process costs for the oxide coating formation are investigated using a design of experiments (DOE). An analysis of variance (ANOVA) is conducted to assess the significance of the parameters for the coating and process properties. For the considered range of the process parameters a significant enhancement of thickness, hardness and wear resistance of the coatings alters also energy consumption during anodic oxidation and process costs, which are assessed by material flow cost accounting (MFCA). Keywords: Anodic oxidation, Aluminium, Energy efficiency, Hardness, Ductility

With the progress in materials science and production technology and the establishment of light-weight design in many fields of the industry, the application of light metals no longer requires only mechanical strength, but also a significant protection of the material against wear and corrosion. Hard and wear-resistant oxide coatings on aluminium are produced by plasma electrolytic oxidation (PEO). During PEO, a conversion of the aluminium substrate to a ceramic oxide takes place. While the role of strength-giving alloying elements like Cu, Mg/Si, Zn, and Zn/Cu on the PEO process has selectively been subject of investigation in the past, the significance of the alloy composition for the service properties of the coatings is still unknown. Therefore, the performance of PEO coatings produced on the widely used commercial high-strength alloys AlCu4Mg1 (EN AW-2024), AlMgSi1 (EN AW-6082), and AlZn5.5MgCu (EN AW-7075) is examined with regard to their behaviour in the rubber-wheel test according to ASTM G65 and the current density-potential behaviour of the substrates with undamaged and worn coatings in dilute NaCl solution. To give a reference to the unalloyed material the testings were carried out also on Al 99.5 (EN AW-1050) which was treated in an adjusted PEO process. Although differences in the conversion of intermetallic phases during PEO and the phase composition of the coatings on the various substrates are determined, the service properties are hardly depending on the alloying elements of the investigated aluminium materials. The wear rates in the rubber-wheel test are low for all the alloyed samples. The current density-potential curves show a decrease of the corrosion current density by approximately one order of magnitude compared to the bare substrate. Eventually, previous wear of the coatings does not deteriorate the corrosion behaviour. PEO layers on technically pure aluminum can resist the testing regimes if they are prepared in an electrolyte with an elevated silicate content and without additional hydroxide ions, during a longer process time.

The anodic oxidation process is an established means for the improvement of the wear and corrosion resistance of high-strength aluminum alloys. For high-strength aluminum-copper alloys of the 2000 series, both the current efficiency of the anodic oxidation process and the hardness of the oxide coatings are significantly reduced in comparison to unalloyed substrates. With regard to this challenge, recent investigations have indicated a beneficial effect of nitric acid addition to the commonly used sulphuric acid electrolytes both in terms of coating properties and process efficiency. The present work investigates the anodic oxidation of the AlCu4Mg1 alloy in a sulphuric acid electrolyte with additions of nitric acid as well as oxalic acid as a reference in a full-factorial design of experiments (DOE). The effect of the electrolyte composition on process efficiency, coating thickness and hardness is established by using response functions. A mechanism for the participation of the nitric acid additive during the oxide formation is proposed. The statistical significance of the results is assessed by an analysis of variance (ANOVA). Eventually, scratch testing is applied in order to evaluate the failure mechanisms and the abrasion resistance of the obtained conversion coatings.

Thermoplastic hybrid laminates are a novel class of material compounds that offer the possibility for large-scale production routes. The laminates consist of an assembly of fiber-reinforced semi-finished layers and metallic sheets in an alternating arrangement. Through the targeted combination of the individual sub-components, a high performing lightweight material with tailor-made properties is achieved. The paper focuses on an advanced thermoplastic hybrid laminate of the CAPAAL type, which is made up of continuous carbon fiber-reinforced polyamide sheets, aluminum top sheets and with continuous glass fiber-reinforced polyamide interlayers in between. The mechanical performance under quasi-static and 3-point bending fatigue, the corresponding damage as well as failure mechanisms are investigated. Under quasi-static bending, a comparatively high stiffness (52 GPa) and strength (645 MPa) in comparison to the commercially established thermosetting hybrid laminates were achieved while even at high strains no interfacial delamination was observed. The bending fatigue tests show that pure elastic loading of the laminate is below the fatigue limit and the laminate withstands one million load cycles without any measurable damages in the individual sub-components. Higher loads are leading to crack propagation inside the aluminum top sheet, whereas only the highest loads applied induced additional damage occurrence inside the thermoplastic matrix. For the first time, investigations on the mechanical performance of a CAPAAL type hybrid laminate under fatigue bending loads are presented. Hereby, in combination with the fast manufacturability of the laminate as a semi-finished product and its subsequent high formability, the suitability for e.g. automotive applications is demonstrated.

In the areas of automotive, aeronautics and civil structures, lightweight construction is a current and a future need. Thus, multi material design has rapidly grown in importance, especially hybrid materials based on fiber reinforced plastics and aluminum offer great potential. Therefore, mechanical interlocking is a convenient way of designing the interface. Laser structuring is already used to generate a variety of surface topographies leading to high bond strengths. This paper investigates different laser structures aiming on highest joint strengths for aluminum and glass fiber reinforced polyamide 6 interfaces. Self-organizing pin structures comprised by additional micro/nano features as well as drilled hole structures, both ranging on the micrometer range, are compared to corundum blasting as a standard method for surface conditioning. For the presented surface structures, thermal joining and ultrasonic assisted joining are regarded towards their potential for an optimum joint design.

Ni-Al2O3 composite coatings electrodeposited from Watt’s electrolyte include Al2O3 nano-and submicron particles. The effect of particle size and concentration of the particles in the electrolyte were investigated on the morphology and incorporation value of particles into the deposits. The influence of alumina particles on the electrodeposition behavior of Ni was also studied by means of electrochemical impedance spectroscopy. The results achieved from the impedance measurements and the correlation with the layer characterization could help to better understand the codeposition mechanism derived from the impact of different particle characteristics including size and concentration on the nature of the double-layer. The increase in the concentration of particles from 1 to 20 g/l resulted in an increase of the double-layer capacity and decrease of the charge transfer resistance, while the addition of submicron particles had a higher influence on the characteristics of the double-layer compared to the nano particles. Although the alumina particles with submicron size could stimulate the incorporation of particles faster than those with nano size, the strengthening performance of the layers not only depended on the incorporation value of the particles, but also on the microstructure of the deposits.

There are various opportunities to improve the adhesion between polymer and metal in metal-plastic composites. The addition of a bonding agent which reacts with both joining components at the interfaces of the composite can enhance the bonding strength. An alternative method for the adjustment of interfaces in metal-plastic composites is the specific surface structuring of the joining partners in order to exploit the mechanical interlock effect. In this study the potential of using an adhesion promoter based on twin polymerization for metal-plastic composites in combination with different methods of mechanical surface treatment is evaluated by using the tensile shear test. It is shown that the new adhesion promoter has a major effect when applied on smooth metal surfaces. A combination of both mechanical and chemical surface treatment of the metal part is mostly just as effective as the application of only one of these surface treatment methods.

Hybrid parts, which combine low weight with high strength, are moving into the focus of the automotive industry, due to their high potential for usage in the field of crash-relevant structures. In this contribution, the development of an intrinsic hybrid composite is presented, with a focus on the manufacturing process, complex simulations of the material behaviour and material testing. The hybrid composite is made up of a continuous fibre- reinforced plastic (FRP), in which a metallic insert is integrated. The mechanical behaviour of the individual components is characterised. For material modelling, an approach is pointed out that enables modelling at large strains by directly connected rheological elements. The connection between the FRP and the metallic insert is realised by a combination of form fit and adhesive bonds. On the one hand, adhesive bonds are generated within a sol gel process. On the other hand, local form elements of the metallic insert are pressed into the FRP. We show how these form elements are generated during the macroscopic forming process. In addition, the applied sol gel process is explained. Finally, we consider design concepts for a specimen type for high strain testing of the resulting interfaces.