A process for the simultaneous plasma-electrolytic anodic oxidation (PAO) of a compound consisting of an Al (AlMgSi1) and Mg (AZ31) alloy is introduced. Using this process, an almost uniformly thick, ...compact oxide coating on both compound partners can be produced provided that the narrow window of this process is determined and kept. The most important parameters for the simultaneous plasma anodizing are the composition and conductivity of the used electrolyte, the current density and the process time. A short-time process using high current densities has been found suitable. This process is a promising procedure for the protection of Al- and Mg-based compound surfaces.
► Simultaneous PAO of a compound consisting of an Al (AlMgSi1) and Mg (AZ31) alloy. ► Production of uniformly thick, compact oxide coatings on both compound partners. ► Simultaneous PAO needs short-time processes and high current densities.
The reliable identification of fakes consisting of bronze often presents problems, because traditional methods such as stylistic studies, optical microscopy, chemical analysis or X‐ray diffraction of ...the corrosion may not be conclusive. We present a method that is based on the comparison of the tin isotope ratios 122Sn/116Sn and 117Sn/119Sn in the metal and in the adherent corrosion layer. An artificial patina is usually generated within a short time period. It has been observed that such a procedure leads to a depletion of the light tin isotopes in the corrosion layer, while in naturally corroded authentic archaeological objects no isotopic fractionation has been detected. The method has also been applied to archaeological objects and it could be confirmed, among other examples, that the famous ‘Sky Disc of Nebra’ is authentic.
In the present study, the interfacial microstructure of dissimilar Al/Ti joints formed by a co-extrusion process has been investigated. The material combinations used for the experiments were ...commercially pure aluminium and titanium, respectively, in the alloys EN AW-6082 and TiAl6V4. X-ray diffraction, energy-dispersive X-ray spectroscopy, electron microscopy and electron backscatter diffraction revealed titanium aluminide formation in the interface, the development of deformation bands in the sleeve material, and the occurrence of grain size refinement and twinning in the core material. The results are discussed with respect to the concept of a hard core–soft sleeve co-extrusion comprising plastic deformation to promote solid-state diffusion. The study shows the phase distribution and the microstructural evolution in the bonding zone with the aim to improve the quality of the bonding by adequately adjusting the process parameters.
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.
Abstract
Within this work, aluminum is oxidized via plasma-electrolytic oxidation (PEO) in the presence of organic substances, including reactive monomers. The aim of this approach is to generate ...polymers and simultaneously bind them to the surface of the freshly generated oxide layers. For this purpose, sheets of aluminum were immersed into electrolytes that comprised either 4 % of sodium acrylate or 10 % of sodium benzoate. The aluminum sheets were oxidized by anodic pulse current at 0.25 A/cm
2
for 30–90 s. By this process, predominantly oxidic conversion layers were produced. The presence of the monomers in the electrolyte influenced the passivation and discharge behavior and finally the microstructure of the layers. It further gave rise to organic material in the layer. In particular, infrared attenuated total reflection spectroscopy (ATR-IR) and X-ray photoemission spectroscopy (XPS) show that layers which were generated in the presence of acrylate or benzoate comprised -C-C-, -C=C-, -C-O, and C=O bonds.
Abstract
Direct powder rolling (DPR) can be used to create metallic sheet at a reduced cost compared to traditional methods. The process is particularly relevant for metals that are beneficiated to a ...powder form. The DPR process, however, is not yet optimised and the material properties corresponding to DPR sheet do not compare well with sheet produced from rolled metallic billet. This study explores the effect of DPR input parameters on DPR aluminium sheet material properties. Roll speed, roll gap, sintering time and sintering temperature are shown to have an impact on the density, microstructure, hardness and ductility of DPR aluminium strip. It is shown that a low roll speed and a small roll gap produced the most dense strip. A roll gap of 0.7 mm and roll speed of 0.366 rpm produced green strip with a density of 90% of cast aluminium while a roll gap of 0.8 mm and roll speed of 0.73 rpm produced green strip with a density of 79.6% of cast aluminium. In addition, a Vickers hardness analysis and a three-point bending test show that increasing the sintering temperature of the green DPR strip will produce softer aluminium strips with higher ductility, as expected.
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.
► Main goal: Development of new Fe-based, wear-resistant materials. ► Strategy: Particle reinforcement with CrB2 by means of high-energy milling (HEM). ► Wear-resistant coatings are produced by thermal spraying (HVOF, APS). ► Combination of nanocrystalline precipitations and microscaled reinforcement particles. ► Result: Excellent resistance against abrasive wear.
The work focuses on the potential of structural and chemical examinations by scanning electron microscopy based methods for archaeometric studies on ceramics. Achieved by a single preparation ...technique (polished block sections), the feasibility and benefits of electron backscatter diffraction are demonstrated as case studies using polychrome examples of pre‐Columbian pottery (Wari, Moche and Cajamarca). Elemental and phase maps allow for separate consideration of clay and temper. Identification of mineral phases and intergrowths of temper particles provide information for clarifying clay procurement and firing techniques with respect to local versus non‐local pottery to enlighten trade relations, technological transfer and shared heritage of pre‐Columbian cultures.
Plasma nitriding is a state-of-the-art thermochemical treatment, which is used by the processing industry for hardening of the surface-near material volumes of tools and components. An artificial ...neural network, particularly backpropagation neural network, has been developed to investigate the hardness behavior of different steel types according to various process parameters. Therefor eleven steels with different chemical compositions were plasma nitrated with different concentrations of nitrogen at various temperatures. The hardness profiles were studied with indentation measurement. The experimental data were used to train the neural network with the Levenberg-Marquardt algorithm. For an optimal training, weight distribution, hidden neurons and gradients of neuron activation functions were varied, to allow simulations of hardness profiles for the different types of steel with deviant nitriding parameters.
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