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Volume Change Effects during Solidification of Alloys
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. (Casting of Metals)
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Volume change during solidification is an important concept in achieving of casting soundness. The solidification shrinkage can cause different defects in the ingot casting as well as the shape casting. The volume change due to phase transformation during solidification is the other concept which has to be studied. In addition, the solidification shrinkage can be affected by the volume change of liquid metals due to the structure change of liquid.

In this work, first, the solidification shrinkage was measured in copper-lead base alloys by a dilatometer which was developed to use for melting and solidification processes. The volume change was measured during primary solidification and monotectic reaction. The macrostructure evaluation of samples was used to explain the volume change results. A shrinkage model was used to explain the volume changes during solidification. In addition, the microsegregation of alloying elements was studied in the alloys.

 

In the second part, the solidification of brass alloys was investigated in different cooling rates. Microstructure evaluation showed that the peritectic transformation occurred as diffusionless (partitionless) as well as the diffusion-controlled transformation. In addition, the volume change was measured in the peritectic alloys. A theoretical analysis was developed to evaluate the volume change effect on the peritectic reaction.

 

Hot crack formation was investigated during the solidification of peritectic steels as a volume change concept during the transformation of ferrite to austenite. A series of in situ solidification experiments was performed using a MTS tensile testing machine combined with a mirror furnace to measure the sample temperature and the force change during solidification. It was observed that a rise in tensile force began with the start of solidification and suddenly dropped. The sudden drop of force, which occurred around the peritectic temperature of the alloy, was accompanied by a crack or a refilled crack in the microstructure. Furthermore, the peritectic reaction types were studied theoretically and experimentally to understand their effects on the force change during solidification. The analyses showed that the volume change due to the peritectic transformation is a reason for crack formation. In addition, when the peritectic reaction occurred as a diffusionless manner (partitionless), the crack formation is more probable.

 

In the last study, the effect of cooling rate and super heat temperature were studied on the precipitation of primary silicon in Al-Si hypereutectic alloys. The liquidus temperature was found to decrease with cooling rate. In addition, the fraction of primary silicon decreased with increasing the cooling rate and the super heat temperature. Furthermore, the morphology of the primary silicon changed as an effect of cooling rate and super heat temperature. It was concluded that the solidification characteristic and silicon morphology relate to the liquid structure.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2009. , xii, 46 p.
Series
Trita-MG, ISSN 1104-7127 ; 2009:3
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-10527ISBN: 978-91-7415-351-4 (print)OAI: oai:DiVA.org:kth-10527DiVA: diva2:218833
Public defence
2009-06-12, F3, Lindstedtsvägen 26, KTH, 13:00 (English)
Opponent
Supervisors
Note
QC 20100726Available from: 2009-06-04 Created: 2009-05-25 Last updated: 2011-03-21Bibliographically approved
List of papers
1. On solidification shrinkage of copper-lead and copper-tin-lead alloys
Open this publication in new window or tab >>On solidification shrinkage of copper-lead and copper-tin-lead alloys
2009 (English)In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 22, no 1-4, 179-182 p.Article in journal (Refereed) Published
Abstract [en]

Solidification shrinkage is an important concept in achieving sound castings. In the present work solidification shrinkage was studied in copper-lead and copper-lead-tin alloys. A series of solidification experiments was performed under different cooling rates using a dilatometer which was developed for melting and solidification purposes. The volume change was measured during primary solidification and the monotectic reaction. In order to explain the volume-changing results, the sample macrostructures were studied to evaluate gas and shrinkage cavities which were formed during the solidification. Furthermore, the volume fraction of the primary phase during solidification was evaluated in the samples that were quenched from different temperatures below the liquidus temperature. A shrinkage model was used to explain the volume changes during solidification.

Keyword
Solidification, Shrinkage, Cu-Pb alloy, Cu-Pb-Sn alloy
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-14198 (URN)10.1179/136404609X367632 (DOI)000268395500044 ()2-s2.0-70350510911 (Scopus ID)
Note
QC 20100726 2nd International Conference on Advances in Solidification Process, Graz, AUSTRIA, JUN 17-20, 2008Available from: 2010-07-26 Created: 2010-07-26 Last updated: 2017-12-12Bibliographically approved
2. Microsegregation and Solidification Shrinkage of Copper-Lead Base Alloys
Open this publication in new window or tab >>Microsegregation and Solidification Shrinkage of Copper-Lead Base Alloys
2009 (English)In: Advances in Materials Science and Engineering, ISSN 1687-6822Article in journal (Refereed) Published
Abstract [en]

Microsegregation and solidification shrinkage were studied on copper-lead base alloys. A series of solidification experiments was performed, using differential thermal analysis (DTA) to evaluate the solidification process. The chemical compositions of the different phases were measured via energy dispersive X-ray spectroscopy (EDS) for the Cu-Sn-Pb and the Cu-Sn-Zn-Pb systems. The results were compared with the calculated data according to Scheil's equation. The volume change during solidification was measured for the Cu-Pb and the Cu-Sn-Pb systems using a dilatometer that was developed to investigate the melting and solidification processes. A shrinkage model was used to explain the volume change during solidification. The theoretical model agreed reasonably well with the experimental results. The deviation appears to depend on the formation of lattice defects during the solidification process and consequently on the condensation of those defects at the end of the solidification process. The formation of lattice defects was supported by quenching experiments, giving a larger fraction of solid than expected from the equilibrium calculation.

Place, publisher, year, edition, pages
Hindawi Publishing Corporation, 2009
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-14204 (URN)10.1155/2009/627937 (DOI)000207890900001 ()2-s2.0-80052654138 (Scopus ID)
Note
QC 20100726Available from: 2010-07-26 Created: 2010-07-26 Last updated: 2012-01-18Bibliographically approved
3. On solidification and shrinkage of brass alloys
Open this publication in new window or tab >>On solidification and shrinkage of brass alloys
2009 (English)In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 22, no 1-4, 183-186 p.Article in journal (Refereed) Published
Abstract [en]

The solidification process was investigated in brass alloys containing a wide range of zinc, between 32.5 and 47.1 wt-%. A series of solidification experiments was performed under different cooling rates using differential thermal analysis (DTA) and a confocal mirror furnace. The cooling rate and the solidification under cooling temperature were evaluated from cooling curves. Furthermore, the peritectic reaction was studied in view of the starting and the ending temperatures and shrinkage behaviour. The volume change was measured in the peritectic alloys using a dilatometer which was developed to investigate the melting and solidification processes. A theoretical analysis was developed to evaluate the volume change effect on the peritectic reaction.

Keyword
Solidification, Shrinkage, Peritectic reaction, Cu-Zn alloy
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-14200 (URN)10.1179/136404609X367623 (DOI)000268395500045 ()2-s2.0-70350521131 (Scopus ID)
Note
QC 20100726 2nd International Conference on Advances in Solidification Process, Graz, AUSTRIA, JUN 17-20, 2008Available from: 2010-07-26 Created: 2010-07-26 Last updated: 2017-12-12Bibliographically approved
4. Hot crack formation during peritectic reaction in steels
Open this publication in new window or tab >>Hot crack formation during peritectic reaction in steels
2010 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 37, no 1, 63-72 p.Article in journal (Refereed) Published
Abstract [en]

Hot crack formation during solidification was investigated during the peritectic reaction in steels. A series of in situ solidification experiments was performed using a MTS tensile testing machine combined with a mirror furnace. Sample temperature and force change were measured during the solidification process. The force measurements showed a sudden drop during the solidification of samples, which occurred around the peritectic temperature of the alloy, were accompanied by cracks or refilled cracks in the microstructure. Furthermore, the peritectic reaction types were studied theoretically and experimentally to understand their effects on the force change during solidification. The theoretical analyses showed that the volume change due to the peritectic transformation is one of the reasons for crack formation. In addition, when the peritectic reaction occurs in a diffusionless (partition less) manner in an alloy with sufficiently high primary precipitation, crack formation is more probable.

Keyword
Hot crack, Peritectic reaction, Steel alloy
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-14201 (URN)10.1179/030192309X12506804200429 (DOI)000273918200010 ()2-s2.0-77949457560 (Scopus ID)
Note
QC 20100726Available from: 2010-07-26 Created: 2010-07-26 Last updated: 2017-12-12Bibliographically approved
5. A study of shell growth irregularities in continuously cast 310S stainless steel
Open this publication in new window or tab >>A study of shell growth irregularities in continuously cast 310S stainless steel
2009 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 36, no 7, 521-528 p.Article in journal (Refereed) Published
Abstract [en]

Growth irregularities in continuous casting are believed to be associated with crack formation and breakouts. Differential thermal analysis on 310S stainless steel samples indicated primary precipitations of both austenite and ferrite during solidification. In tensile tests on solidifying samples, abrupt shrinkages in volume were detected in the peritectic range of temperatures. Micrographic and microsegregation analysis on samples extracted from a breakout shell revealed high ratios of primary-precipitated austenite in the thick sections of the shell, and high ratios of primary-precipitated ferrite in the thin sections. Alternating precipitations of austenite and ferrite are proposed to occur during solidification. Regions of the shell with high ratios of primary austenite remain in contact with the mould and exhibit high growth rates, whereas regions with high ratios of primary ferrite shrink in volume due to the ferrite to austenite transformation, which results in the formation of air gaps between the shell and the mould and reductions in growth rate.

Keyword
Growth irregularities, Continuous casting, Stainless steel, Peritectic, Precipitation, Shrinkage
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-14202 (URN)10.1179/174328109X445714 (DOI)000270918600005 ()2-s2.0-77949457784 (Scopus ID)
Note
QC 20100726Available from: 2010-07-26 Created: 2010-07-26 Last updated: 2017-12-12Bibliographically approved
6. On solidification of hypereutectic Al-Si alloys
Open this publication in new window or tab >>On solidification of hypereutectic Al-Si alloys
2009 (English)In: Transactions of the Indian Institute of Metals, ISSN 0019-493X, Vol. 62, no 4-5, 361-365 p.Article in journal (Refereed) Published
Abstract [en]

Precipitation of primary silicon was studied in Al-Si hypereutectic alloys with 15, 18, and 25 wt. % silicon content. The alloys were solidified with different cooling rates from different super heat temperatures. The liquidus and eutectic temperature were evaluated from the cooling curves. The liquidus temperature was found to decrease with cooling rate. The evaluation of microstructure showed that the fraction of primary silicon decreased with increasing the cooling rate and super heat temperature. Furthermore, the morphology of the primary silicon changed as an effect of cooling rate and super heat temperature.

Keyword
hypereutectic Al-Si alloy, solidification, bcooling rate, super heat
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-14203 (URN)000276133700022 ()2-s2.0-76249083519 (Scopus ID)
Note
QC 20100726Available from: 2010-07-26 Created: 2010-07-26 Last updated: 2017-12-12Bibliographically approved

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