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Imperfections in Recycled Aluminium-Silicon Cast Alloys
Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
2015 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

In striving to produce high quality cast components from recycled aluminium alloys,imperfections have to be considered, because recycled aluminium usually containsmore of it. However, there are great energy savings to be made by using recycledaluminium; as little as 5% of the energy needed for primary aluminium productionmay be required. High quality castings are dependent on, besides alloy chemistry, bothmelt quality and the casting process; the focus of this work is related to the meltquality.This thesis aims to increase knowledge about imperfections, foremost about Fe-richparticles, oxides/bifilms, and porosity. Experiments were performed at industrialfoundry facilities and in a laboratory environment. Melt quality was evaluated byproducing samples with the reduced pressure test (RPT), from which both densityindex (DI) and bifilm index (BI) could be measured, results that were related to tensiletest properties. Data from tensile test samples were analysed, and fracture surfacesand cross sections were studied in both light microscope and in scanning electronmicroscope (SEM). For the purpose of investigating nucleation of primary Fe-richparticles (sludge) differential scanning calorimetry (DSC) was used.In the analysis of results, a correlation between the morphology of particles and tensileproperties were found. And elongated Fe-rich β-particles were seen to fracturethrough cleavage towards the centre. However, DI and BI have not been possible torelate to tensile properties.The nucleation temperature of primary Fe-rich particles were found to increase withincreased Fe, Mn, and Cr contents, i.e. the sludge factor (SF), regardless of cooling rate.For a set SF, an increase of cooling rate will decrease the nucleation temperature.

Ort, förlag, år, upplaga, sidor
Jönköping: Jönköping University, School of Engineering , 2015. , s. 39
Serie
JTH Dissertation Series ; 8
Nyckelord [en]
Imperfections, Recycled cast Al-Si alloy, Fe-rich particles, Melt quality, Fractography, Differential scanning calorimetry.
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
URN: urn:nbn:se:hj:diva-26790ISBN: 978-91-87289-09-5 (tryckt)OAI: oai:DiVA.org:hj-26790DiVA, id: diva2:814725
Presentation
2015-06-12, E1405, Jönköping University, School of Engineering, Jönköping, 10:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2015-06-01 Skapad: 2015-05-28 Senast uppdaterad: 2017-01-09Bibliografiskt granskad
Delarbeten
1. On the complexity of the relationship between microstructure and tensile properties in cast aluminum
Öppna denna publikation i ny flik eller fönster >>On the complexity of the relationship between microstructure and tensile properties in cast aluminum
2015 (Engelska)Ingår i: International Journal of Modern Physics B, ISSN 0217-9792, Vol. 29, nr 10-11, artikel-id 1540011Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The relationship between microstructure and mechanical properties in cast aluminium alloys is very complex. This relationship is also strongly affected by the casting process and melt handling. In the current study the mechanical properties were investigated and correlated with microstructural features such as porosity, Fe-rich particles, SDAS, Si-length. Process quality measures such as bifilm index, density index, and sludge factor were also investigated. The aim of the work was to understand the critical interactions between material microstructure and process quality in the development of high performance materials.

Nyckelord
imperfections, defects, porosity, fe-rich, sdas, silicon, bifilm, density, sludge, mechanical, properties, aluminium, aluminum
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
urn:nbn:se:hj:diva-24687 (URN)10.1142/S0217979215400111 (DOI)000353523600012 ()2-s2.0-84928555789 (Scopus ID)
Konferens
Asia Pacific Conference on Materials Processing 2014
Tillgänglig från: 2014-12-23 Skapad: 2014-09-09 Senast uppdaterad: 2017-12-05Bibliografiskt granskad
2. Assessment of Quality when Delivering Molten Aluminium Alloys Instead of Ingots
Öppna denna publikation i ny flik eller fönster >>Assessment of Quality when Delivering Molten Aluminium Alloys Instead of Ingots
2013 (Engelska)Ingår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 765, s. 266-270Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Recycled aluminium alloys manufactured at Stena Aluminium, in Älmhult, Sweden, are delivered in special designed transport containers, called thermoses. Thermoses are best described as an insulating layer protected by a steel cover with a heat loss of about 5 degrees/h. Three thermoses are transported by a truck, giving the possibility for a total capacity of about 24 tonnes delivered aluminium just-in-time to the foundry. By delivering a full load of liquid aluminium, about 2 tonnes of carbon dioxide emissions are saved, compared with delivering ingots. The aim of the paper is to assess the quality benefits, in terms of inclusions sedimentation and mechanical properties, assured by delivering aluminiummelts instead of ingots. The results indicate that materials produced by just-in-time melt delivery have slightly improved quality compared to ingots. The trends are explained in terms of quality, density and bifilm indexes, based on microstructural observations as well as tensile test data analysis.

Ort, förlag, år, upplaga, sidor
Trans Tech Publications, 2013
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
urn:nbn:se:hj:diva-20256 (URN)10.4028/www.scientific.net/MSF.765.266 (DOI)2-s2.0-84882945035 (Scopus ID)978-3-03785-766-3 (ISBN)
Konferens
6th International Light Metals Technology Conference, LMT 2013; Old Windsor; United Kingdom; 24 July 2013 through 26 July 2013
Forskningsfinansiär
KK-stiftelsen
Tillgänglig från: 2013-01-17 Skapad: 2013-01-17 Senast uppdaterad: 2018-09-13Bibliografiskt granskad
3. On the formation of sludge intermetallic particles in secondary aluminum alloys
Öppna denna publikation i ny flik eller fönster >>On the formation of sludge intermetallic particles in secondary aluminum alloys
2015 (Engelska)Ingår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 46, nr 8, s. 3713-3722Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The primary precipitation of Fe-rich intermetallics in AlSi9Cu3(Fe) type alloys is studied for different Fe, Mn, and Cr contents and cooling rates. Differential scanning calorimetry, thermal analysis, and interrupted solidification with a rapid quenching technique were used in combination in order to assess the nucleation temperature of sludge particles, as well as to follow their evolution. The results revealed that the sludge nucleation temperature and the release of latent heat during sludge formation are functions of Fe, Mn, and Cr levels in the molten alloy (i.e., the sludge factor, SF) and cooling rate. Moreover, it can be concluded that sensitivity to sludge formation is not affected by cooling rate; i.e., a decrease in the SF will reduce sludge nucleation temperature to the same extent for a higher cooling rate as for a lower cooling rate. The sludge formation temperature detected will assist foundries in setting the optimal molten metal temperature for preventing sludge formation in holding furnaces and plunger systems.

Ort, förlag, år, upplaga, sidor
Springer, 2015
Nyckelord
aluminium alloys, sludge factor, Fe-rich intermetallics, DSC, thermal analysis
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
urn:nbn:se:hj:diva-22716 (URN)000356728100039 ()2-s2.0-84932195555 (Scopus ID)
Tillgänglig från: 2013-12-13 Skapad: 2013-12-13 Senast uppdaterad: 2018-06-08Bibliografiskt granskad

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