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Willam S. Miller

Bio: Willam S. Miller is an academic researcher from Tata Steel. The author has contributed to research in topics: Aluminium & Isothermal process. The author has an hindex of 4, co-authored 8 publications receiving 2511 citations.

Papers
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Journal ArticleDOI
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.

1,955 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated new processing routes and new alloy chemistries for aircraft materials, which offer major improvements in ductility, toughness, fatigue performance and in reduction of residual stress in large dimension plate and sheet products.
Abstract: Driven by the increasing requirements from aircraft producers, Hoogovens Aluminium Rolled Products GmbH, together with Hoogovens Research & Development, has enhanced the property combinations of their aircraft materials. For these types of material, optimised processing routes as well as new alloy chemistries have been investigated. Whilst retaining the strength levels required by the aerospace industry, new processing routes offer major improvements in ductility, toughness, fatigue performance and in reduction of residual stress in large dimension plate and sheet products. A further goal of investigating new alloy chemistries is the trend towards new joining techniques such as welding and brazing for aircraft structures. These new joining techniques require different property combinations compared to the conventional aerospace alloys. In parallel to these improved processing routes and new alloy developments, new ultrasonic inspection techniques have been developed, which are able to predict fatigue performance and residual stress in thick plate products.

990 citations

Journal ArticleDOI
TL;DR: In this article, the authors focus on investigations performed to optimise the process for high strength AA7xxx high strength thick plates in aerospace applications, including the measurement of quench rate within thick plates, quench factor analysis, simulation of the effect of changes in quench practice on final properties and modelling work of residual stress.
Abstract: The aircraft industry is constantly striving for improved materials which enables higher performance at reduced cost. The development of high speed milling machines and improvements in thick plate properties regarding distortion during machining have led to the conclusion that large machined structures can replace forged components and significantly reduce the cost by reducing the number of components and joints. For this reason, Hoogovens Aluminium Rolled Products together with Hoogovens Research and Development, has continued to improve the property balance required for AA7xxx high strength thick plates in aerospace applications. This paper will focus on investigations performed to optimise the process for high strength thick plates. This work contains a careful analysis of the process steps including the measurement of quench rate within thick plates, quench factor analysis, simulation of the effect of changes in quench practice on final properties and modelling work of residual stress to gain the best property balance required for thick plates in aerospace applications. Finally, the improved mechanical properties and the low level of distortion during machining for high strength thick plates will be discussed.

4 citations


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Journal ArticleDOI
20 Sep 2017-Nature
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

Journal ArticleDOI
TL;DR: In this paper, the current research status of microstructure, properties and heat treatment of SLM processing aluminum alloys is systematically reviewed respectively and a future outlook is given at the end of this review paper.

642 citations

Journal ArticleDOI
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

Journal ArticleDOI
01 Oct 2015-Nature
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

Journal ArticleDOI
TL;DR: In this paper, the development history and applications of Al-Li alloys over the last few years are reviewed, and the main issue of anisotropic behavior of all the alloys is discussed.

360 citations