Abstract: This paper provides an overview of the main issues related to the durability of aluminium alloy structures. In particular, the main corrosion pathways are considered, in relation to alloy type, microstructural features, thermomechanical treatments and environmental characteristics. The strategies for corrosion mitigation are also discussed, with particular focus on the tailoring of anodizing treatments for enhanced durability.
Abstract: Light weight as a primary factor in combination with strength and durability properties of aluminium alloys brings financial benefits accruing not only from material procurement but along the whole chain of production, manufacturing, delivery and installation, maintenance and even disposal. A significant contribution in the quest to deliver more value has been the development in the last decade of harmonized design and execution standards, the Eurocodes, National Annexes and adapted codes or recommendations for specific applications. The sustainability issue can be dealt with in a more reliable way due to the comprehensive data tools and comparative analyses available nowadays. Experience with growing numbers of applications also delivers benchmark values for initial cost and maintenance requirements.
Abstract: The paper deals with the applications of aluminium alloys in the main structures used in the Offshore Industry. The reasons why aluminium and its alloys are the suitable materials for this kind of applications are clearly identified. After mentioning the appropriate standards and design rules, some important examples, like helicopter decks, gangways and living quarters, are illustrated in details. An overview on the typical connecting systems of aluminium alloys commonly used for the offshore technology is presented.
Abstract: Among the Aluminum casting processes, High Pressure Die Casting (HPDC) is an efficient, versatile and economic way for producing large number of components. Nevertheless, because of the elevated amount of rejected castings, it is important to know which are the main causes of defect formation and their effects on microstructure and mechanical properties. This paper presents, within the European MUSIC project, an overview of the preliminary correlations obtained studying both castings with defect generator geometry, referred to as Horse-shoe Reference Castings, and industrial demonstrators, referred to as Gear Box Housing. The deduced correlations between static mechanical properties and casting defects highlighted interesting trends in both cases.
Abstract: 2XXX and 7XXX high strength aluminum alloys are the most used materials for structural parts of aircrafts due to their high strength/weight ratio. Their joining procedure is an engineering challenge since they present low weldability. Friction Stir Welding (FSW) is a joining technology developed in the early 90 ́s. It is a solid-state welding process, without the use of fillers or gas shield, that eliminates conventional welding defects and has been considered of great interest for application in the aircraft industry. FSW of aluminum alloys results in four regions of different microstructures, specifically: the base material (BM), the heat affected zone (HAZ), the thermo-mechanically affected zone (TMAZ), and the nugget zone (NZ). The complex microstructure of the weld region leads to higher susceptibility to localized corrosion as compared to the BM even when similar alloys are joined. The welding of dissimilar alloys in its turn results in even more complex microstructures as materials with intrinsically different composition, microstructures and electrochemical properties are put in close contact. Despite the great interest in FSW, up to now, only few corrosion studies have been carried out for characterization of the corrosion resistance of dissimilar Al alloys welded by FSW. The aim of this study is to investigate the corrosion behavior of aluminum alloy 2024-T3 (AA2024-T3) welded to aluminum alloy 7475-T761 (AA7475-T761) by FSW. The evaluation was performed in 0.01 mol.L-1 by means of open circuit potential measurements, polarization techniques and surface observation after corrosion tests.
Abstract: In the past five years a number of master’s theses have been conducted at Belgian Technical Colleges and Universities to (re)introduce knowledge of aluminium as a structural material, given that courses offered in Belgium are oriented towards steel and concrete design and no specific course on aluminium exists. The present contribution highlights the different subjects covered in these theses and illustrates the results obtained. Emphasis is placed on the methodology used to design and innovate with aluminium, taking into account the Eurocode rules that apply to the design of specific aluminium structures. For this, appropriate use was made of existing software that allows for the detailed calculation of section reduction and unity checks.
Abstract: The role played by transition elements and rare earths, added in small quantities (fractions of unity in weight percent) was proved by several authors to be beneficial for the age-hardening response and for the microstructural stability at high temperature of Al-based alloys. The paper illustrates the results of an experimental investigation on the effects of erbium (Er) additions on the microstructural features, microstructural stability and mechanical properties of an Al-7Si-0.4Mg alloy of wide industrial use. The effects are multifold: in the cast microstructure, a silicon (Si) eutectic modification was observed with the formation of several Er-containing intermetallic phases. After solution treatment and aging, an increase in peak hardness and an enhanced microstructural stability were obtained. In this preliminary study, the beneficial effects of Er additions were confirmed.
Abstract: In this work, we propose a new approach to producing ultrafine grained plates using a modified ECAP method, namely incremental ECAP. Unlike conventional ECAP, incremental ECAP works step by step whereby deformation and feeding are performed with two different tools acting asynchronously. Incremental processing reduces forces and allows to process relatively large billets. The major advantage of this technique is that the specimens are in the form of plates with a rectangular shape, which makes them suitable for further processing, e.g. via deep drawing. This paper reports a study on microstructure development, mechanical properties and their anisotropy in aluminium plates processed by means of incremental ECAP. Eight passes applied (with the accumulated strain of 9.2) with the rotation about the Z axis brought about the reduction in the grain size down to 600 nm with the 80% fraction of high angle grain boundaries and a very homogenous equiaxial microstructure. This, in turn, resulted in a significant increase in mechanical strength with the ultimate tensile strength reaching 200 MPa and, more importantly, very low anisotropy with respect to the rolling direction.
Abstract: Sandwich foam beams, made of solid skins and aluminium foam core, are usually applied in high-tech engineering field while they are not yet adopted in civil structures. An initial, explorative study on the structural application of metal foam is presented in this paper. The potentials of sandwich foam beams are studied through analytical models and parametric analyses; the sensitivity of the flexural response of the media to the total amount of pores and their spatial distribution are investigated. An analytical tool able to design functionally graded beams of metallic foam is presented and applied with reference some commercial aluminium foams. An experimental campaign is being planned to validate the presented results.