Abstract: Within the last decade, Friction Stir Welding (FSW) has increasingly been gaining relevance for joining nonferrous metals, especially aluminum alloys. Possible applications range from the aerospace and automotive sector up to manufacturing electrical components. Compared to conventional fusion welding processes, FSW offers numerous advantages, as it for example does not require shielding gas or filler material. However, FSW is still not applied or taken into account during the product development process in proportion to its potential. This is mainly caused by the lack of data in order to evaluate the process economically and differentiate it to other processes like arc and laser welding, also regarding technological factors. Therefore, this investigation focusses on the possibilities and limits when joining wrought and cast aluminum alloys, like EN AW-6082 T6, EN AW-7075 T651 and AlSi11Mg0,3, respectively, by FSW compared to MIG. The weld quality of the samples is characterized by tensile testing, hardness measurements and microstructure analysis. Furthermore, an approach to reduce the process forces by using FSW tools with reduced diameters and respectively adjusted process parameters is presented.
Abstract: This study focuses on the modelling of Flow-Drill Screw (FDS) connections in large-scale shell analyses. Macroscopic connection models for large-scale crash simulations were assessed for modelling of FDS connections between two aluminium plates. Of the investigated models were two commercial element-based and three commercial constraint-based models, as well as two new user-defined element-based models. All models were calibrated using cross tests in tension, shear and a mixed shear/tension mode. In order to assess the flexibility of the models two sets of experimental data were used. In the first one, a small screw was used to join two sheets of the same rolled alloy while the second set used a longer screw with a larger head to join a rolled alloy to an extrusion. The calibrated models were validated using a two-step approach involving benchmark and component tests. Of the commercial models, the constraint-based performed better than the element-based. The new user-defined models gave similar results as the commercial constraint-based models. From the obtained results, recommendations for modelling of FDS connections for large-scale analyses were formulated.
Abstract: It is difficult to join dissimilar materials such as metallic material and polymer. We have investigated to join Aluminum alloy and high density polyethylene (PE) and ethylene acrylic acid copolymer (EAA) using Friction Lap Joining (FLJ) and then concluded EAA could be strongly joined with Aluminum alloy. PE could not be joined without anodizing. We have considered that EAA has a polar functional group, COOH. On the contrary, PE cannot be joined to an as-received aluminum alloy, because PE has no polar functional group. So, we have tried to confirm this mechanism with XPS and FTIR to investigate the interface between anodized surface and that of polymer. We find that the possibility of chemical bonding arises between O-H in COOH and O in Al2O3or O in C=O and O in Al2O3 at elevated temperature.
Abstract: Since the invention of the friction stir welding, several studies have been conducted to understand the influence of process parameters on the microstructural, thermal and mechanical characteristics to improve the weld quality. Banded structures better known under the name of "onion rings" are one of phenomena that appear in the microstructure during this process. The welding parameters leading to their appearance as well as their effect on the quality of the joint are still subject to much research with different conclusions. In this context, the objective of this research work is to determine various characteristics of the ‘onion rings’ and correlate them to processing conditions.
Abstract: A company recently reported, the unexpected and sudden failure of several containers, fabricated from aluminium 8006 and sealed using a polymeric film. The failure resulted when there was a loss of adhesion at the metal/polymeric lid interface, making the containers unusable. Some preliminary adhesion tests have highlighted that, containers, coming from various production batches and sealed using the same kind of lid, exhibited different adhesion strengths. To investigate the cause of the detachment of the lid from the edge of the container, the following parameters has been considered: (i) the iron content of the Al alloy, (ii) the effect of lubricant oil at the polymeric film/substrate interface, (iii) the topography of the contact surface between the lid and the container. The electrochemical behaviour of Al8006 was investigated by means of potentiodynamic polarization tests, both in an aerated aqueous solution of Na2SO4 (0.5 M) and in an aerated aqueous solution of NaCl (0.6 M). The results revealed a significant increase in corrosion rate for the samples with higher iron content, as well as the negative influence of oil on the surface. Roughness measurements have confirmed the importance of the surface profile: a surface showing Sku>3, provides better adhesion. Metallographic measurements demonstrated that high iron content in the alloy results in the development of numerous corrosion spots and prevents good adhesion between the sealant polymeric film and the aluminium foil.
Abstract: The effect of hydrothermal treatment time on sealing and corrosion resistance of the AA7475-T761 anodized aluminium alloy has been investigated in this study. The hydrothermal treatments tested are environmental compatible without chromium ions involved. Anodizing was carried out by a tartaric-sulphuric anodizing (TSA) process and this was followed by hydrothermal treatments for partial sealing, in various solutions. The effect of propyleneglycol (PRG) and/or cerium ions in the hydrothermal treatment solution was evaluated. Four treatment times were tested, specifically, 2.5, 5.0, 7.5 and 10 min. The corrosion resistance of the anodized and treated samples was evaluated by Electrochemical Impedance Spectroscopy (EIS) and the anodic layers formed were characterized by Scanning Electron Microscopy (SEM). The EIS results showed that the hydrothermal treatments in solutions with cerium ions resulted in similar impedances for periods of treatment from 5 to 10 min whereas in the solutions with PRG the impedance increased with time of treatment from 2.5 to 10 min showing a slower kinetics of anodic layer sealing. However, the fastest kinetics of sealing were associated to the treatments that combined two steps, one in PRG and other in cerium containing solutions with similar impedances obtained from 2.5 to 10 min of treatment. Surface evaluation by SEM showed that the porosities in the anodic layer were not sealed for the periods of hydrothermal treatments corresponding to 2.5 min. The presence of cerium in hydrothermal treatment had a beneficial effect on the stability of the anodic layer formed and provided a healing effect on the corroding sites.
Abstract: The aim of this paper is to investigate about the Portevin-Le Chatelier Effect (PLC) on a AA 5083 sheet. In order to study the minimizing of the PLC effect, three different rolling cyles have been carried out and an experimental campaign on the three different AA 5083 rolled has been carried out. In particular, the experimental campaign, to better understand the evolution of the phenomena during the rolling process, is based on: microstructural analysis, tensile tests and fractographic observations. Finally it has been found that the greater grain size the smaller the PLC effect, even if this effect cannot be totally removed, furthermore the PLC effect occurs only in the rolling direction. The best rolling cycle is the one that provide a hot rolling until 4mm, then a cold rolling up to 2mm and a final heat treatment of annealing.
Abstract: Coil Coating is an advanced finishing technology available for different metal substrates, specifically steel and aluminum, with several millions of square meters processed each year. Born in the 60’s, the coil coating technology has gained interest in the market in the late 80’s and 90’s and it’s now booming due its peculiarities both technical as well as environmental and in terms of energy. The Coil Coated product is used in many different applications’ fields: architecture, with facades, cladding, industrial and residential roofing, shutters: transportation, with caravan, train interiors; industry, with caps, closures. The same application technology is widely used for canstock – body, ends and taps: the process concept, being the same, though with remarkable differentiation in terms of speed, metal gauges, application systems and paint qualities (water based, low gauge and highly diluted). The process and the product are both very complex: the Product consists of a combination merging metal, surface treatment and paints; the Process is thus a combination of different steps, perfectly synchronized unique in terms of speed and contact time. Metallurgy, Chemistry, Mechanics, Fluid Dynamics, Energy management: this all comes together within seconds on the same line. For Aluminum, the product features depends on metal alloy – usually 1xxx, 3xxx and 5xxx, with the most different tempers ranging from fully soft through fully hard; different paint types and qualities, ranging from standard Polyester, through the newly developed HDPE and Polyurethane with / without Polyamide to high quality PVdF and Fluopolymers. The presentation will detail these technical features highlighting the significant differences between traditional finishing and Coil Coating
Abstract: In the flexible food packaging industry, producers of laminated aluminium predominantly use a "rinse" technology for surface treatments characterized by very bulky machinery. The Laminazione Sottile Group togehther with the University of Naples Federico II and the gscsg have developed and characterized a new, extremely simplified, process that provides a "no rinse" treatment on aluminium alloy AA8079Y. In addition, this treatment is chromium free, because chromium has been replaced by zirconium salts. The characteristics of resistance have been verified by using Electrochemical Impedance Spectroscopy (EIS) and cathodic delamination tests. Results obtained show that the "no rinse" treatment with zirconium salts produces an effective protective effect.
Abstract: The cold spray technology is an innovative technique used to coat metallic and non-metallic substrates for protection from corrosion and/or to improve surface functionalities. It is well known that surface degradation (i.e. corrosion) is not merely an aesthetic issue; its consequences may affect the structural behaviour and the usability of structures or parts of them. This paper addresses the use of cold spray technology as a potential innovative tool for the repair of an extruded 6005A-T6 aluminium alloy item. The specimens investigated have a complex geometry and are used for a new kind of bolt-channel joints to secure the passenger seats to the frame of buses. In order to simulate environmental degradation, samples were exposed to aerated synthetic seawater for 15, 60 and 240 days and, subsequently, cold spray coated using a pure aluminium powder. Results acquired show that layers obtained using Cold Spray process are effective against corrosion, restore volume and geometry shape of corroded metals components without showing visible traces of the repair.