Recent development in aluminium alloys for the automotive industry
15 Mar 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing (Elsevier)-Vol. 280, Iss: 1, pp 37-49
TL;DR: In this paper, the authors present a review of recent developments in aluminium alloys to improve formability, surface quality in both 5000 and 6000 alloys, and the bake hardening response of 6500 alloys.
Abstract: The growing demand for more fuel-efficient vehicles to reduce energy consumption and air pollution is a challenge for the automotive industry. The characteristic properties of aluminium, high strength stiffness to weight ratio, good formability, good corrosion resistance, and recycling potential make it the ideal candidate to replace heavier materials (steel or copper) in the car to respond to the weight reduction demand within the automotive industry. This paper summarises the recent developments covering aluminium’s use in castings, extrusions and sheet; two specific examples will be given. The first deals with hang-on parts manufactured by Hoogovens Rolled Products Duffel, for which the weight saving potential can be 50%. Currently, the highly formable 5000 alloys are used mostly for inner panel applications, whilst the heat-treatable 6000 alloys are preferred for outer panel applications. This presentation reviews recent developments in aluminium alloys to improve formability, surface quality in both 5000 and 6000 alloys, and the bake hardening response of 6000 alloys. It also indicates the trend to develop a unialloy system to improve the aluminium scrap recycling. The second area deals with brazing sheet. Over the last 10 years there has been an increasing trend to replace copper heat exchangers with ones manufactured from brazed aluminium. Hoogovens Aluminium Walzprodukte Koblenz is one of the world’s leading supplier of aluminium brazing sheet and is in the forefront of developing alloys with the combination of strength, formability, brazing performance and long life required by its customers. Materials have been development for both vacuum and controlled atmosphere brazing. The current status and future trends in aluminium brazing sheet for automotive applications will be presented. Particular emphasis has been placed on the development of long life alloys with superior corrosion performance over the more conventional materials. Using these two examples the technical and commercial aspects of the manufacturing processes of aluminium automotive components and engineering design support of materials producers are illustrated. The essential feature is the close co-operation at all stages between the material’s supplier and the automotive manufacture.
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TL;DR: The approach to metal-based additive manufacturing is applicable to a wide range of alloys and can be implemented using a range of additive machines, and provides a foundation for broad industrial applicability, including where electron-beam melting or directed-energy-deposition techniques are used instead of selective laser melting.
Abstract: Metal-based additive manufacturing, or three-dimensional (3D) printing, is a potentially disruptive technology across multiple industries, including the aerospace, biomedical and automotive industries. Building up metal components layer by layer increases design freedom and manufacturing flexibility, thereby enabling complex geometries, increased product customization and shorter time to market, while eliminating traditional economy-of-scale constraints. However, currently only a few alloys, the most relevant being AlSi10Mg, TiAl6V4, CoCr and Inconel 718, can be reliably printed; the vast majority of the more than 5,500 alloys in use today cannot be additively manufactured because the melting and solidification dynamics during the printing process lead to intolerable microstructures with large columnar grains and periodic cracks. Here we demonstrate that these issues can be resolved by introducing nanoparticles of nucleants that control solidification during additive manufacturing. We selected the nucleants on the basis of crystallographic information and assembled them onto 7075 and 6061 series aluminium alloy powders. After functionalization with the nucleants, we found that these high-strength aluminium alloys, which were previously incompatible with additive manufacturing, could be processed successfully using selective laser melting. Crack-free, equiaxed (that is, with grains roughly equal in length, width and height), fine-grained microstructures were achieved, resulting in material strengths comparable to that of wrought material. Our approach to metal-based additive manufacturing is applicable to a wide range of alloys and can be implemented using a range of additive machines. It thus provides a foundation for broad industrial applicability, including where electron-beam melting or directed-energy-deposition techniques are used instead of selective laser melting, and will enable additive manufacturing of other alloy systems, such as non-weldable nickel superalloys and intermetallics. Furthermore, this technology could be used in conventional processing such as in joining, casting and injection moulding, in which solidification cracking and hot tearing are also common issues.
1,670 citations
TL;DR: In this paper, the use of natural fiber composites, produced in developing countries, has presented several social, environmental and economical advantages to design “green” automotive components.
511 citations
TL;DR: Enhanced ductility can be achieved by increasing the time and temperature at which the transition from the easy-glide metastable dislocation to the immobile basal-dissociated structures occurs, as well as the underlying insights needed to guide the design of ductile magnesium alloys.
Abstract: Magnesium is a lightweight structural metal but it exhibits low ductility-connected with unusual, mechanistically unexplained, dislocation and plasticity phenomena-which makes it difficult to form and use in energy-saving lightweight structures. We employ long-time molecular dynamics simulations utilizing a density-functional-theory-validated interatomic potential, and reveal the fundamental origins of the previously unexplained phenomena. Here we show that the key 〈c + a〉 dislocation (where 〈c + a〉 indicates the magnitude and direction of slip) is metastable on easy-glide pyramidal II planes; we find that it undergoes a thermally activated, stress-dependent transition to one of three lower-energy, basal-dissociated immobile dislocation structures, which cannot contribute to plastic straining and that serve as strong obstacles to the motion of all other dislocations. This transition is intrinsic to magnesium, driven by reduction in dislocation energy and predicted to occur at very high frequency at room temperature, thus eliminating all major dislocation slip systems able to contribute to c-axis strain and leading to the high hardening and low ductility of magnesium. Enhanced ductility can thus be achieved by increasing the time and temperature at which the transition from the easy-glide metastable dislocation to the immobile basal-dissociated structures occurs. Our results provide the underlying insights needed to guide the design of ductile magnesium alloys.
450 citations
Cites background from "Recent development in aluminium all..."
...The increased forest density also decreases the slip rate directly in equation (1)....
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...Around room temperature, the fast transition of easy-glide Æc 1 aæ dislocations into immobile basal-dissociated Æc 1 aæ or Æcæ dislocations acts to (1) rapidly decrease the density of mobile Æc 1 aæ dislocations rm and (2) rapidly increase the density of immobile/forest dislocations ra’ f affecting all slip systems....
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...For nucleating strengthening precipitates, Cd was not used because it was unable to improve the intergranular fracture of alloy 2020 [59,60]....
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TL;DR: In this paper, room temperature and elevated temperature experiments were conducted on a tensile split Hopkinson bar apparatus to identify the constitutive response and damage evolution in AA5754 and AA5182 aluminum alloy sheet at high strain rates.
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References
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TL;DR: In this paper, Auger electron spectroscopy and vaporization methods have been used in studying the mechanism of brazing to elucidate the characteristics of the oxide film barrier and magnesium promoter.
Abstract: Fluxless vacuum brazing has become a commercially feasible process for the high‐volume, low‐cost production of aluminum heat exchangers. With an Al–Si–Mg filler metal, excellent joint quality is obtained without requiring the use of a flux. A limited understanding of the wetting and flow characteristics of the filler alloy and the role of the magnesium promoter in the vacuum process, however, have hampered efforts to optimize control of the vacuum process. Auger electron spectroscopy and vaporization methods have been used in studying the mechanism of brazing to elucidate the characteristics of the oxide film barrier and magnesium promoter. With these methods it is possible to follow the distinctive variations in surface composition and magnesium vaporization rate that occur in the braze sheet as a function of its temperature. The mechanistic details of the wetting and flow processes in this commercially important material are delineated in the results.
27 citations
01 Feb 1978
TL;DR: A non-corrosive flux for furnace brazing of aluminum involves a non-hygroscopic potassium fluoroaluminate material having a melting point near but below that of the filler material.
Abstract: A new non-corrosive flux for furnace brazing of aluminum involves a non-hygroscopic potassium fluoroaluminate material having a melting point near but below that of the filler material. This flux dissolves or disrupts the oxide skin on the aluminum surface, does not react with aluminum, and has a substantially water-insoluble residue after brazing. The process confers the benefits of a conventional flux in terms of tolerance to fit up and cleanliness, but with the advantage of eliminating flux removal postbraze treatments. When used in an inert gas mode, it has a significant tolerance to impurities in the furnace atmosphere. It has no detrimental effect on the corrosion resistance of the brazed product, and indeed has an inhibiting effect. The material and the process are promising as being economical and reliable for brazing automotive heat exchangers.
23 citations
01 Feb 1987
21 citations
18 citations