Structure and Defect Formation during DC Casting of Aluminium Alloys

Research activities on aluminium production technology focus on the successive steps in the production chain of aluminium wrought products. Direct-chill casting of aluminium alloys is a well-developed technology with a long history. But only in the last 20 years, the development of computer modelling offered a means of better understanding of the physical phenomena involved in solidification. The main scientific challenge is to obtain a fundamental insight into the processing of aluminium alloys and to establish quantitative relationships between materials, processes, and performance. A systems approach is employed, covering theoretical and experimental studies on processing into semi-finished products. Special emphasis is placed on experimental verification and industrial applicability with the availability of pilot scale experimental facilities at M2i-TUD. This facilitates the design of process conditions as desired for experimental validation studies. In this paper we will consider main mechanisms of structure and defect formation during solidification of DC cast billets, mostly based in the results obtained in cooperation between Delft University of Technology and Materials Innovation Institute (M2i).

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Improved VDC Casting of Aluminium Alloys through an Understanding of the Surface Properties of the Molten Metal

Materials Science Forum ◽

10.4028/www.scientific.net/msf.519-521.1693 ◽

2006 ◽

Vol 519-521 ◽

pp. 1693-1698

Author(s):

John A. Taylor ◽

Ian F. Bainbridge

Keyword(s):

Surface Properties ◽

Molten Metal ◽

Aluminium Alloys ◽

Defect Formation ◽

Direct Chill ◽

Gradual Change ◽

Liquid Aluminium ◽

Hot Top ◽

Metal Head ◽

Wide Range

Vertical direct chill (VDC) casting of aluminium alloys is a mature process that has evolved over many decades through gradual change to both equipment design and casting practice. Today, air-pressurised, continuous lubrication, hot top mould systems with advanced station automation are selected as the process of choice for producing extrusion billet. Specific sets of operating parameters are employed on these stations for each alloy and size combination to produce optimal billet quality. The designs and parameters are largely derived from past experience and accumulated know-how. Recent experimental work at the University of Queensland has concentrated on understanding the way in which the surface properties of liquid aluminium alloys, e.g., surface tension, wetting angle and oxide skin strength, influence the size and shape of the naturally-stable meniscus for a given alloy, temperature and atmosphere. The wide range of alloyand condition-dependent values measured has led to the consideration of how these properties impact the stability of the enforced molten metal meniscus within the hot top mould cavity. The actual shape and position of the enforced meniscus is controlled by parameters such as the upstream conduction distance (UCD) from sub-mould cooling and the molten metal head. The degree of deviation of this actual meniscus from the predicted stable meniscus is considered to be a key driver in surface defect formation. This paper reports on liquid alloy property results and proposes how this knowledge might be used to better design VDC mould systems and casting practices.

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Assessing the Exergetic and Inherent Safety Performance of a Shrimp-Based Biorefinery via Computer-Aided Tools

Energies ◽

10.3390/en13246688 ◽

2020 ◽

Vol 13 (24) ◽

pp. 6688

Author(s):

Kariana Andrea Moreno-Sader ◽

Jairo David Martínez-Consuegra ◽

Ángel Darío González-Delgado

Keyword(s):

Large Scale ◽

Pilot Scale ◽

Point Of View ◽

Safety Performance ◽

Process Conditions ◽

Inherent Safety ◽

Process Data ◽

Production Chain ◽

Processing Wastes ◽

Exergy Losses

Although shrimp processing wastes have been studied as source of high-value products at lab-scale, no contributions are found in the literature regarding the energetic and safety performance of shrimp-based biorefineries at pilot or large-scale. This works is focused on the inherent safety assessment and exergy analysis of a pilot-scale biorefinery designed to produce shrimp meat and four by-products: chitin, chitosan, nitrogenous extract, and astaxanthin. Total irreversibilities, exergy losses, exergy of wastes and utilities were calculated for stages and the overall process using mass and energy balances of the biorefinery. The hazards associated with chemicals and process conditions were analyzed through substance properties and process data. A Numerical Descriptive Inherent Safety Technique (NuDIST) score of 557.23 suggested a moderate level of risk for the biorefinery compared to other processes, reaching chemical and process safety scores of 185.88 and 371.35, respectively. Sections (b) and (c) were identified as major hotspots from a safety point of view. The overall exergy efficiency was quantified at 25.61%, which is higher than the chitosan-from-exoskeleton linear production chain (4.58%). The highest exergy losses were found on stages as deacetylation, fresh shrimp washing and deproteinization stages. The beheading stage most contributed to irreversibilities, with 98.315%, followed by sorting, with 1.653%. These results could identify opportunities for improvement from an exergy and safety point of view by mapping less efficient and hazardous stages.

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Local Anesthetics and Recurrence after Cancer Surgery-What’s New? A Narrative Review

Journal of Clinical Medicine ◽

10.3390/jcm10040719 ◽

2021 ◽

Vol 10 (4) ◽

pp. 719

Author(s):

Sarah D. Müller ◽

Jonathan S. H. Ziegler ◽

Tobias Piegeler

Keyword(s):

Tumor Cells ◽

Circulating Tumor Cells ◽

Local Anesthetics ◽

Experimental Studies ◽

Perioperative Period ◽

Cancer Surgery ◽

Narrative Review ◽

Future Research ◽

Inflammatory Stress ◽

Research Activities

The perioperative use of regional anesthesia and local anesthetics is part of almost every anesthesiologist’s daily clinical practice. Retrospective analyses and results from experimental studies pointed towards a potential beneficial effect of the local anesthetics regarding outcome—i.e., overall and/or recurrence-free survival—in patients undergoing cancer surgery. The perioperative period, where the anesthesiologist is responsible for the patients, might be crucial for the further course of the disease, as circulating tumor cells (shed from the primary tumor into the patient’s bloodstream) might form new micro-metastases independent of complete tumor removal. Due to their strong anti-inflammatory properties, local anesthetics might have a certain impact on these circulating tumor cells, either via direct or indirect measures, for example via blunting the inflammatory stress response as induced by the surgical stimulus. This narrative review highlights the foundation of these principles, features recent experimental and clinical data and provides an outlook regarding current and potential future research activities.

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THE INTERACTION BETWEEN TOOL MATERIAL, ENVIRONMENT, AND PROCESS CONDITIONS IN THE MACHINING OF ALUMINIUM ALLOYS

Machining Science and Technology ◽

10.1080/10940349908945694 ◽

1999 ◽

Vol 3 (2) ◽

pp. 273-286 ◽

Cited By ~ 5

Author(s):

W. Y. H. Liew ◽

I.M. Hutchings ◽

J. A. Williams

Keyword(s):

Aluminium Alloys ◽

Tool Material ◽

Process Conditions ◽

Material Environment

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Application of Biofilm Kinetics to Anaerobic Fixed Bed Reactors

Water Science & Technology ◽

10.2166/wst.1991.0584 ◽

1991 ◽

Vol 23 (7-9) ◽

pp. 1319-1326 ◽

Cited By ~ 4

Author(s):

I. E. Gönenç ◽

D. Orhon ◽

B. Beler Baykal

Keyword(s):

Removal Rate ◽

Fixed Bed ◽

Experimental Studies ◽

Pilot Scale ◽

Cod Removal ◽

Experimental Results ◽

Fixed Bed Reactor ◽

Removal Mechanism ◽

Term Operation ◽

Fixed Bed Reactors

Two basic phenomena, reactor hydraulics and mass transport through biofilm coupled with kinetic expressions for substrate transformations were accounted for in order to describe the soluble COD removal mechanism in anaerobic fixed bed reactors. To provide necessary verification, experimental results from the long term operation of the pilot scale anaerobic reactor treating molasses wastewater were used. Theoretical evaluations verified by these experimental studies showed that a bulk zero-order removal rate expression modified by diffusional resistance leading to bulk half-order and first-order rates together with the particular hydraulic conditions could adequately define the overall soluble COD removal mechanism in an anaerobic fixed bed reactor. The experimental results were also used to determine the kinetic constants for practical application. In view of the complexity of the phenomena involved it is found remarkable that a simple simulation model based on biofilm kinetics is a powerful tool for design and operation of anaerobic fixed bed reactors.

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Equilibrium modeling of mono and binary sorption of Cu(II) and Zn(II) onto chitosan gel beads

Chemical and Process Engineering ◽

10.1515/cpe-2016-0040 ◽

2016 ◽

Vol 37 (4) ◽

pp. 485-501 ◽

Cited By ~ 1

Author(s):

Józef Nastaj ◽

Małgorzata Tuligłowicz ◽

Konrad Witkiewicz

Keyword(s):

Metal Ion ◽

Ph Value ◽

Experimental Studies ◽

Process Conditions ◽

Optimal Process ◽

Sorption Data ◽

Gel Beads ◽

Two Component ◽

Equilibrium Data ◽

Chitosan Gel

Abstract The objective of the work are in-depth experimental studies of Cu(II) and Zn(II) ion removal on chitosan gel beads from both one- and two-component water solutions at the temperature of 303 K. The optimal process conditions such as: pH value, dose of sorbent and contact time were determined. Based on the optimal process conditions, equilibrium and kinetic studies were carried out. The maximum sorption capacities equaled: 191.25 mg/g and 142.88 mg/g for Cu(II) and Zn(II) ions respectively, when the sorbent dose was 10 g/L and the pH of a solution was 5.0 for both heavy metal ions. One-component sorption equilibrium data were successfully presented for six of the most useful three-parameter equilibrium models: Langmuir-Freundlich, Redlich-Peterson, Sips, Koble-Corrigan, Hill and Toth. Extended forms of Langmuir-Freundlich, Koble-Corrigan and Sips models were also well fitted to the two-component equilibrium data obtained for different ratios of concentrations of Cu(II) and Zn(II) ions (1:1, 1:2, 2:1). Experimental sorption data were described by two kinetic models of the pseudo-first and pseudo-second order. Furthermore, an attempt to explain the mechanisms of the divalent metal ion sorption process on chitosan gel beads was undertaken.

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Direct chill billet casting of aluminium alloys

Solidification and Casting ◽

10.1201/9781420033502-2 ◽

2016 ◽

pp. 3-25

Author(s):

Martin Jarrett ◽

Bill Neilson ◽

Estelie Manson-Whitton

Keyword(s):

Aluminium Alloys ◽

Direct Chill

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Friction Stir Welding of Elements Made of Cast Aluminium Alloys

Archives of Metallurgy and Materials ◽

10.2478/amm-2014-0064 ◽

2014 ◽

Vol 59 (1) ◽

pp. 385-392

Author(s):

B. Rams ◽

A. Pietras ◽

K. Mroczka

Keyword(s):

Friction Stir Welding ◽

Aluminium Alloy ◽

Aluminium Alloys ◽

Welding Parameters ◽

Process Conditions ◽

Friction Stir ◽

Seam Weld ◽

Cast Aluminium ◽

Weld Structure ◽

Welding Stability

Abstract The article presents application of FSW method for joining elements made of cast aluminium alloys which are hardly weldable with other known welding techniques. Research’s results of plasticizing process of aluminium and moulding of seam weld during different FSW process’ conditions were also presented. Influence of welding parameters, shape and dimensions of tool on weld structure, welding stability and quality was examined. Application of FSW method was exemplified on welding of hemispheres for valves made of cast aluminium alloy EN AC-43200.

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