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Bjurenstedt, A., Ghassemali, E., Seifeddine, S. & Dahle, A. (2019). The effect of Fe-rich intermetallics on crack initiation in cast aluminium: an in-situ tensile study. Materials Science & Engineering: A, 756, 502-507
Open this publication in new window or tab >>The effect of Fe-rich intermetallics on crack initiation in cast aluminium: an in-situ tensile study
2019 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 756, p. 502-507Article in journal (Refereed) Published
Abstract [en]

To evaluate the role of Fe-rich intermetallics on crack initiation, two fully modified Al-Si alloys, one containing plate-like β-Fe and the second containing primary α-Fe intermetallics, were investigated by in-situ tensile testing in the scanning electron microscope. In the first alloy, large plate-like β-Fe intermetallics oriented parallel to the test direction were the first to crack at an elongation of about 1.8%. More transversely oriented intermetallics caused crack initiation in the matrix which linked up with the final fracture. In the second alloy, the cracking of α-Fe intermetallics initiated at an elongation of about 0.9%. It is concluded that large α-Fe intermetallics crack first and that clusters of α-Fe are the most potent crack initiation sites.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Al-Si alloy, Cast aluminium, Fracture mechanics, Tensile testing in SEM, α-Fe, β-Fe, Aluminum alloys, Crack initiation, Cracks, Fracture testing, Intermetallics, Materials testing apparatus, Metal testing, Scanning electron microscopy, Silicon alloys, Tensile testing
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-36962 (URN)10.1016/j.msea.2018.07.044 (DOI)000469893400058 ()2-s2.0-85064717473 (Scopus ID)
Available from: 2017-08-21 Created: 2017-08-21 Last updated: 2019-06-20Bibliographically approved
Riestra, M., Bjurenstedt, A., Bogdanoff, T. & Ghassemali, E. (2018). Complexities in the assessment of melt quality. Paper presented at Symposium on Light Metals Alliance - Light Metals Technology (LMT) held during the Conference on Materials Science and Technology (MS and T), October 8, 2017, Pittsburgh, PA, USA. International Journal of metalcasting, 12(3), 441-448
Open this publication in new window or tab >>Complexities in the assessment of melt quality
2018 (English)In: International Journal of metalcasting, ISSN 1939-5981, E-ISSN 2163-3193, Vol. 12, no 3, p. 441-448Article in journal (Refereed) Published
Abstract [en]

If high-performance aluminium castings are to be produced, the melt quality needs to be properly assured. Multiple tests for melt quality assessment exist and have previously been analysed. In most studies, the techniques were used separately. In this work, reduced pressure, fluidity, Prefil and tensile tests were evaluated. A commercial EN 46000 alloy was used as the base material with additions of 25 and 50 wt% machining chips to degrade the melt quality. In reduced pressure and fluidity tests, oxides floated to the top of samples, decreasing the reliability. Bifilm index increased with addition level, but not correspondingly. Density index, Prefil and fluidity tests did not present significant variations, and tensile properties only deteriorated with the 50 wt% addition level. The investigated techniques provided information, but measuring the melt quality reliably remains a challenge.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
melt quality; reduced pressure test; fluidity; tensile properties; Prefil; hydrogen content
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-38003 (URN)10.1007/s40962-017-0179-y (DOI)000436927100005 ()2-s2.0-85049321529 (Scopus ID)
Conference
Symposium on Light Metals Alliance - Light Metals Technology (LMT) held during the Conference on Materials Science and Technology (MS and T), October 8, 2017, Pittsburgh, PA, USA
Available from: 2017-11-28 Created: 2017-11-28 Last updated: 2019-02-14Bibliographically approved
Bjurenstedt, A., Casari, D., Seifeddine, S., Mathiesen, R. H. & Dahle, A. K. (2017). In-situ study of morphology and growth of primary α-Al(FeMnCr)Si intermetallics in an Al-Si alloy. Acta Materialia, 130, 1-9
Open this publication in new window or tab >>In-situ study of morphology and growth of primary α-Al(FeMnCr)Si intermetallics in an Al-Si alloy
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2017 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 130, p. 1-9Article in journal (Refereed) Published
Abstract [en]

Morphology and growth of primary α-Al(FeMnCr)Si intermetallics have been studied in-situ during solidification of a commercial secondary aluminum alloy employing X-radiographic imaging combined with deep-etching. The α-Al(FeMnCr)Si intermetallics were found to nucleate primarily on surface oxides, and the continued growth yielded both rhombic dodecahedrons and elongated rod-like morphologies. Both morphologies were observed as hopper and massive types, where the hopper intermetallics had the higher growth rates. The growth rate, which determines the type, appears to be linked to nucleation frequency; higher nucleation frequency promoted massive types and lower nucleation frequency promoted hopper intermetallics. 

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Aluminum, Casting, Crystal growth, Intermetallics, Primary α-Al(FeMnCr)Si, Aluminum alloys, Hoppers, Morphology, Nucleation, Silicon, Silicon alloys, Deep etching, In-Situ Study, Nucleation frequencies, Rhombic dodecahedron, Rod-like morphology, Secondary aluminum, Surface oxide, X-radiographic imaging
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-35343 (URN)10.1016/j.actamat.2017.03.026 (DOI)000401388700001 ()2-s2.0-85015790499 (Scopus ID)JTHMaterialIS (Local ID)JTHMaterialIS (Archive number)JTHMaterialIS (OAI)
Available from: 2017-04-10 Created: 2017-04-10 Last updated: 2017-08-21Bibliographically approved
Bjurenstedt, A. (2017). On the influence of imperfections on microstructure and properties of recycled Al-Si casting alloys. (Doctoral dissertation). Jönköping: Jönköping University, School of Engineering
Open this publication in new window or tab >>On the influence of imperfections on microstructure and properties of recycled Al-Si casting alloys
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There are great energy savings to be made by recycling aluminium; as little as 5% of the energy needed for primary aluminium production may be required. Striving to produce high quality aluminium castings requires knowledge of microstructural imperfections, which is extra important when casting recycled aluminium that generally contains higher levels of imperfections compared to primary aluminium. Imperfections include amongst others Si, Fe, and Mn as well as oxides. Si is needed for castability, but it may also initiate fracture. There are different types of Fe-rich intermetallics influencing properties of castings, generally in a negative direction. Oxides constitute cracks and they are elusive because they are difficult to quantify.

This thesis aims to increase knowledge about imperfections in recycled aluminium castings originating from alloying elements and the melt. Experiments were performed in advanced laboratory equipment, including X-radiographic imaging during solidification and in-situ tensile testing in a scanning electron microscope. Experiments were also performed at industrial foundry facilities.

The experiments showed that the nucleation temperature of primary α-Fe intermetallics increased with higher Fe, Mn, and Cr contents. Primary α-Fe are strongly suggested to nucleate on oxides and to grow in four basic morphologies. Lower nucleation frequency of α-Fe promoted faster growth and hopper crystals while higher nucleation frequency promoted slower growth rates and massive crystals. Results also showed that a decrease in the size of the eutectic Si and plate-like β-Fe intermetallics improved tensile properties, foremost the elongation to fracture. In β-Fe containing alloys the transversely oriented intermetallics initiated macrocracks that are potential fracture initiation sites. In alloys with primary α-Fe foremost clusters of intermetallics promoted macrocracks. In fatigue testing, a transition from β-Fe to α-Fe shifted the initiation sites from oxides and pores to the α-Fe, resulting in a decrease of fatigue strength. Oxides in Al-Si alloys continue to be elusive; no correlations between efforts to quantify the oxides and tensile properties could be observed.

Abstract [sv]

Genom att återvinna aluminium kan stora energibesparingar göras eftersom återvinning kan förbruka så lite som 5% av den energi som behövs för produktion av primär aluminium. Vid gjutning av högkvalitativa aluminiumprodukter krävs förståelse för defekter i mikrostrukturen och denna kunskap är extra viktig vid användning av återvunnen aluminium, som i regel innehåller mer defekter än primär aluminium. Defekterna består bland annat av Si, Fe och Mn samt oxider. Si behövs för gjutbarhet men kan också initiera brott. Järnrika intermetaller kan ha olika morfologier som generellt påverkar gjutna komponenter negativt. Oxider, som kan utgöra sprickor, är gäckande då de är svåra att kvantifiera.

Denna avhandlings syfte är att öka kunskapen om defekter i gjutna komponenter av återvunnen aluminium. Experiment utfördes med avancerad laborationsutrustning så som röntgenfotografering av prover under stelning och dragprovning i svepelektronmikroskop. Experiment utfördes också i industrimiljö.

Experimenten visade att kärnbildningstemperaturen steg för primära α-Fe intermetaller med ökade andelar av Fe, Mn och Cr. Resultaten tyder starkt på att primär α-Fe kärnbildas på oxider och att de växer i fyra olika morfologier. Lägre kärnbildningstäthet av α-Fe främjade snabbare tillväxt av kristaller med håligheter men högre kärnbildningstäthet främjade långsammare tillväxt av massiva kristaller. Resultaten visade också att minskad storlek av eutektiskt Si och β-Fe intermetaller ledde till förbättring av dragprovsresultaten, främst brottförlängningen. I legeringar med β-Fe ledde transversellt orienterade intermetaller till makrosprickor vilka kan initiera brott. I legeringar med primär α-Fe var det främst kluster av intermetaller som orsakade makrosprickor. I utmattningsprovning orsakade modifiering av β-Fe till α-Fe förflyttning av sprickinitieringen från oxider och porer till α-Fe, vilket resulterade i en reducerad utmattningshållfasthet. Oxiderna i Al-Si-legeringar fortsätter att gäcka; ingen korrelation mellan försök att kvantifiera oxiderna och draghållfasthet kunde påvisas.

Place, publisher, year, edition, pages
Jönköping: Jönköping University, School of Engineering, 2017. p. 67
Series
JTH Dissertation Series ; 28
Keywords
Imperfections, Recycled Al-Si alloys, Fe-rich intermetallics, Melt quality, Fractography, Defekter, Återvunna Al-Si legeringar, Fe-rika intermetaller, Smältakvalité, Fraktografi
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-36963 (URN)978-91-87289-29-3 (ISBN)
Public defence
2017-09-15, E1405 (Gjuterisalen), Tekniska Högskolan, Jönköping, 10:00
Opponent
Supervisors
Available from: 2017-08-21 Created: 2017-08-21 Last updated: 2017-08-21Bibliographically approved
Ceschini, L., Morri, A., Toschi, S., Boromei, I., Bjurenstedt, A. & Seifeddine, S. (2016). Al-Si-Cu alloys for high pressure die casting: Influence of Fe, Mn, and Cr on room temperaturemechanical properties. Paper presented at High Tech Die Casting 2016, Venice, 22-23 June, 2016.. La Metallurgia Italiana (6), 77-80
Open this publication in new window or tab >>Al-Si-Cu alloys for high pressure die casting: Influence of Fe, Mn, and Cr on room temperaturemechanical properties
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2016 (English)In: La Metallurgia Italiana, ISSN 0026-0843, no 6, p. 77-80Article in journal (Refereed) Published
Abstract [en]

Al-Si-Cu alloys with high Fe content are widely employed in high pressure die casting (HPDC). Even if Feis usually considered an impurity in secondary aluminum alloys, leading to the formation of harmfulintermetallic compounds, it helps in mitigating or eliminating the problem of die soldering. As a result,secondary Al alloys with Fe content of about 1 wt% are commonly employed for the production of HPDCcastings. Aiming to change the morphology of harmful Fe-bearing phases towards less detrimentalmorphologies, proper alloying elements may be added to the alloys. Mn and Cr (both present in thealuminum scrap), as instance, are reported to prevent from the formation of the acicular β-Al5FeSi phase,leading to the formation of more compact and polygonal intermetallics. Such phases are usually referredto as “sludge” particles. The influence of sludge particles on mechanical properties of Al -Si-Cu castings isstill under investigation. The present work aims at evaluating the effect of impurities (Fe, Mn and Cr)typically present in secondary Al alloys on the microstructure and mechanical properties of the A380 (Al -Si-Cu) alloy. Samples with different Fe, Mn and Cr content were produced and processed through adirectional solidification equipment to obtain specimens with controlled SDAS (~10 μm). Hardness androtating bending fatigue tests were carried out at room temperature. Mechanical properties of the alloyswere then related to the microstructure, analyzed by optical and scanning electron microscopy.

Place, publisher, year, edition, pages
Milano: Associazione Italiana di Metallurgia, 2016
Keywords
High pressure die casting, HPDC, Al-Si-Cu alloys, sludge, fatigue, microstructure
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-31423 (URN)2-s2.0-84993960856 (Scopus ID)JTHMaterialIS (Local ID)JTHMaterialIS (Archive number)JTHMaterialIS (OAI)
Conference
High Tech Die Casting 2016, Venice, 22-23 June, 2016.
Available from: 2016-08-22 Created: 2016-08-22 Last updated: 2017-11-28
Bjurenstedt, A., Seifeddine, S. & Jarfors, A. (2016). The effects of Fe-particles on the tensile properties of Al-Si-Cu alloys. Metals, 6(12), Article ID 314.
Open this publication in new window or tab >>The effects of Fe-particles on the tensile properties of Al-Si-Cu alloys
2016 (English)In: Metals, ISSN 2075-4701, Vol. 6, no 12, article id 314Article in journal (Refereed) Published
Abstract [en]

The effect of Fe-rich particles has been a topic for discussion in the aluminum casting industry because of the negative impact they exert on the mechanical properties. However, there are still contradictions on the effects of various morphologies of Fe-particles. In this study, microstructural characterization of tensile tested samples has been performed to reveal how unmodified and modified Fe-rich particles impact on the tensile behavior. Analysis of additions of Fe modifiers such as Mn and Cr, showed higher amounts of primary Fe-rich particles (sludge) with increased porosity and, as result, degraded tensile properties. From the fracture analysis of tensile tested HIPed samples it could be concluded that the mechanical properties were mainly governed by the Fe-rich particles, which were fracturing through cleavage, not by the porosity.

Place, publisher, year, edition, pages
MDPI (Multidisciplinary Digital Publishing Institute), 2016
Keywords
Fe-rich particles, sludge, tensile properties, fracture, casting, solidification, aluminum, silicon, recycling
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-26789 (URN)000389600600020 ()2-s2.0-85007193518 (Scopus ID)
Available from: 2015-05-28 Created: 2015-05-28 Last updated: 2019-02-05Bibliographically approved
Bjurenstedt, A. (2015). Imperfections in Recycled Aluminium-Silicon Cast Alloys. (Licentiate dissertation). Jönköping: Jönköping University, School of Engineering
Open this publication in new window or tab >>Imperfections in Recycled Aluminium-Silicon Cast Alloys
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Jönköping: Jönköping University, School of Engineering, 2015. p. 39
Series
JTH Dissertation Series ; 8
Keywords
Imperfections, Recycled cast Al-Si alloy, Fe-rich particles, Melt quality, Fractography, Differential scanning calorimetry.
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-26790 (URN)978-91-87289-09-5 (ISBN)
Presentation
2015-06-12, E1405, Jönköping University, School of Engineering, Jönköping, 10:00 (English)
Opponent
Supervisors
Available from: 2015-06-01 Created: 2015-05-28 Last updated: 2017-01-09Bibliographically approved
Bjurenstedt, A., Seifeddine, S. & Jarfors, A. (2015). On the complexity of the relationship between microstructure and tensile properties in cast aluminum. Paper presented at Asia Pacific Conference on Materials Processing 2014. International Journal of Modern Physics B, 29(10-11), Article ID 1540011.
Open this publication in new window or tab >>On the complexity of the relationship between microstructure and tensile properties in cast aluminum
2015 (English)In: International Journal of Modern Physics B, ISSN 0217-9792, Vol. 29, no 10-11, article id 1540011Article in journal (Refereed) 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.

Keywords
imperfections, defects, porosity, fe-rich, sdas, silicon, bifilm, density, sludge, mechanical, properties, aluminium, aluminum
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-24687 (URN)10.1142/S0217979215400111 (DOI)000353523600012 ()2-s2.0-84928555789 (Scopus ID)
Conference
Asia Pacific Conference on Materials Processing 2014
Available from: 2014-12-23 Created: 2014-09-09 Last updated: 2017-12-05Bibliographically approved
Ferraro, S., Bjurenstedt, A. & Seifeddine, S. (2015). On the formation of sludge intermetallic particles in secondary aluminum alloys. Metallurgical and Materials Transactions. A, 46(8), 3713-3722
Open this publication in new window or tab >>On the formation of sludge intermetallic particles in secondary aluminum alloys
2015 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 46, no 8, p. 3713-3722Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
Springer, 2015
Keywords
aluminium alloys, sludge factor, Fe-rich intermetallics, DSC, thermal analysis
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-22716 (URN)000356728100039 ()2-s2.0-84932195555 (Scopus ID)
Available from: 2013-12-13 Created: 2013-12-13 Last updated: 2018-06-08Bibliographically approved
Bjurenstedt, A., Seifeddine, S. & Liljenfors, T. (2013). Assessment of Quality when Delivering Molten Aluminium Alloys Instead of Ingots. Paper presented at 6th International Light Metals Technology Conference, LMT 2013; Old Windsor; United Kingdom; 24 July 2013 through 26 July 2013. Materials Science Forum, 765, 266-270
Open this publication in new window or tab >>Assessment of Quality when Delivering Molten Aluminium Alloys Instead of Ingots
2013 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 765, p. 266-270Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
Trans Tech Publications, 2013
National Category
Metallurgy and Metallic Materials
Identifiers
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)
Conference
6th International Light Metals Technology Conference, LMT 2013; Old Windsor; United Kingdom; 24 July 2013 through 26 July 2013
Funder
Knowledge Foundation
Available from: 2013-01-17 Created: 2013-01-17 Last updated: 2018-09-13Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-4005-812X

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