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Microstructural Evolution In As-cast Alloys during Plastic Deformation
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.ORCID iD: 0000-0001-9315-7178
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The effect of deformation on microstructural changes in metals and alloys is the subject of considerable practical interest. The ultimate goal is to control, improve and optimize the microstructure and texture of the finished products produced by metal forming operations. The development in the subject field is remarkable but a more in-depth study could lead us to the better understanding of the phenomena.

 

In the present work microstructural evolution during the plastic deformation of as-cast pure metals and alloys is studied. An experimental method was developed to study the material behavior under the hot compression testing. This method was applied on the as-cast structure of copper, bearing steel, Incoloy 825 and β brass at different temperatures and strain rates. The temperature of the samples was measured during and after the deformation process. The microstructure of the samples was examined by optical microscopy and scanning electron microscopy (SEM). The microstructural evolution during deformation process was investigated by transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). The samples were subsequently subjected to electron microprobe analysis (EMPA) to investigate the effect of the deformation on the microsegregation of Mo, Cr, Si, and Mn.

 

It was observed that the temperature of the samples deformed at strain rates of 5 and 10 s-1 increases abruptly after the deformation stops. However, compression test at the lower strain rates of 1 and 0.5 s-1 revealed that a constant temperature was maintained in the early stage of deformation, followed by an increase until the maximum temperature was obtained. This temperature behavior can be explained by the microstructural evolution during the deformation process. Micrograph analysis revealed the formation of deformation bands (DBs) in highly strained regions. The DBs are highly effective sites for recrystallization. The interdendritic regions are suitable sites for the formation of DBs due to the high internal energy in these regions. EMPA indicated a tendency towards uphill diffusion of Mo in the DBs with increasing strain. The effect of strain on the dissolution of carbides in the band structure of bearing steel was investigated by measuring the volume fraction of carbides inside the band structure at different strain levels. The results indicate that carbide dissolution is influenced by strain. 

 

The microstructural evolution inside the DBs was studied as a function of several properties: temperature, internal energy, and microsegregation. Compression of β brass revealed that twinning is the most prominent feature in the microstructure. EBSD analysis and energy calculations demonstrated that the twinning is not due to a martensitic process but rather the order/disorder transition during the deformation process. The effect of heat treatment at Tc (650°C) prior to deformation on the microstructure of β brass was also investigated, which revealed a relationship between twin formation and the anti-phase domain boundaries

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , 44 p.
Keyword [en]
plastic deformation, compression test, recrystallization, deformation band, As-cast, microsegregation, carbide dissolution, disordered structure, order/disorder transformation, twining, steel, β brass, copper
National Category
Engineering and Technology
Research subject
SRA - E-Science (SeRC)
Identifiers
URN: urn:nbn:se:kth:diva-133362ISBN: 978-91-7501-926-0 (print)OAI: oai:DiVA.org:kth-133362DiVA: diva2:661039
Public defence
2013-11-22, B2, KTH,Royal Institute of technology Brinellvägen23, Stockholm, 14:43 (English)
Opponent
Supervisors
Note

QC 20131104

Available from: 2013-11-04 Created: 2013-10-31 Last updated: 2013-11-04Bibliographically approved
List of papers
1. Disorder Structure formation during plastic defroamtion of pure copper
Open this publication in new window or tab >>Disorder Structure formation during plastic defroamtion of pure copper
2012 (English)In: International journal of material science, ISSN 0973-4589, Vol. 7, no 3, 169-182 p.Article in journal, News item (Refereed) Published
Abstract [en]

The effect of the deformation process at 300˚C on the cast structure of pure copper is investigated. The temperature measurements during compression test are performed by a new experimental method developed earlier [1]. The deformed structure is studied with the aid of optical and transmission electron microscopy. Micrographs show the formation of deformed bands with high internal energy, due to many lattice defects. The strain energy calculations are based on an energy balance and the data obtain from micrograph studies performed by optical and transmission electron microscopy. It is found that there is a significant difference in the strain energy values obtained in the present work compared to the values available in the literature.  The strain energy values obtained in the band structure of the present work are 17.4% to 24% of the heat of fusion of Cu. Such high energy is sufficient to change the normal FCC structure to a disordered atomic structure in the highly deformed regions, during plastic deformation.

Place, publisher, year, edition, pages
Research Indian publication: , 2012
Keyword
disorder structure, plastic defamation, copper
National Category
Metallurgy and Metallic Materials
Research subject
SRA - E-Science (SeRC)
Identifiers
urn:nbn:se:kth:diva-129570 (URN)
Note

QC 20131031

Available from: 2013-10-02 Created: 2013-10-02 Last updated: 2013-11-04Bibliographically approved
2. Effect of deformation on microsegregation in cast structure of bearing steel
Open this publication in new window or tab >>Effect of deformation on microsegregation in cast structure of bearing steel
2012 (English)In: TMS 2012 141st Annual Meeting & Exhibition - Supplemental Proceedings, Vol 2: Materials Properties, Characterization, And Modeling, 2012, Vol. 2, 309-316 p.Conference paper, Published paper (Refereed)
Abstract [en]

Microsegregation changes in the cast structure of a five-ton ingot of ball bearing steel are investigated by a series of hot compression tests. Cylindrical specimens are deformed at a temperature range of 800 degrees C to 900 degrees C and strain rates of 0.5 s(-1). Samples are quenched after the compression in order to eliminate the homogenization time. Subsequently they are analysed with the aid of Electron Microprobe Analysis (EMPA) in order to investigate the effect of hot compression on microsegregation of Mo, Cr, Mn and Si. It is found that highly segregated regions are regions for formation of deformation bands. It seems that the degree of microsegregation increases by increasing the deformation. An attempt is made to estimate the diffusion coefficients of alloying elements during the deformation process. The increase of microsegregation during deformation is explained by tendency for uphill diffusion.

Series
TMS Annual Meeting, 2
Keyword
Cast structure, Diffusion, Microsegregation, Plastic deformation
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-100062 (URN)000311607900040 ()2-s2.0-84860768504 (Scopus ID)978-111829609-7 (ISBN)
Conference
141st Annual Meeting and Exhibition, TMS 2012; Orlando, FL;11 March 2012 through 15 March 2012
Note

QC 20120803

Available from: 2012-08-03 Created: 2012-08-03 Last updated: 2013-11-04Bibliographically approved
3. An Insight into the Effect of Deformation on Carbide Dissolution in the Band Structure of Bearing Steel
Open this publication in new window or tab >>An Insight into the Effect of Deformation on Carbide Dissolution in the Band Structure of Bearing Steel
2013 (English)In: Diffusion In Solids And Liquids VIII, Trans Tech Publications Inc., 2013, 171-176 p.Conference paper, Published paper (Refereed)
Abstract [en]

Dendritic segregation in deformed samples remains in the form of band structure, which is a high-strained region. The present work investigates the effect of the uphill diffusion process, occurring during deformation, on the dissolution of carbide particles in the band structure. A series of hot compression tests are performed on the cast structure of bearing steel by using a hydraulic testing machine, MTS 810. Cylindrical specimens are deformed in a temperature range of 800 degrees C to 900 degrees C and at strain rates of 5s(-1) and 0.5s(-1). In order to eliminate the recovery process, samples are immediately quenched after the compression. The microsegregation of Cr, Mo, Mn and Si are investigated in the band structure, which shows a tendency of uphill diffusion during deformation process. The results show that the volume fraction of carbides varies with the increased straining. The results also show that deformation causes the fragmentation, dispersion of pearlite in the dendrites and the dissolution of spheroidized carbides in the band structure.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2013
Series
Defect and Diffusion Forum, ISSN 1012-0386 ; 334-335
Keyword
cast structure, carbide, diffusion, plastic deformation
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-123134 (URN)10.4028/www.scientific.net/DDF.334-335.171 (DOI)000317868600030 ()2-s2.0-84879812165 (Scopus ID)
Conference
8th International Conference on Diffusion in Solids Liquids (DSL 2012), JUN 25-29, 2012, Istanbul, Turkey
Note

QC 20130604

Available from: 2013-06-04 Created: 2013-06-03 Last updated: 2013-11-04Bibliographically approved
4. Plastic Deformation and Recrystallization in Incoloy 825
Open this publication in new window or tab >>Plastic Deformation and Recrystallization in Incoloy 825
(English)Manuscript (preprint) (Other academic)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-133414 (URN)
Note

QS 2013

Available from: 2013-10-31 Created: 2013-10-31 Last updated: 2013-11-04Bibliographically approved
5. Microstructural Evolution during Deformation of beta Brass
Open this publication in new window or tab >>Microstructural Evolution during Deformation of beta Brass
(English)Manuscript (preprint) (Other academic)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-133415 (URN)
Note

QS 2013

Available from: 2013-10-31 Created: 2013-10-31 Last updated: 2013-11-04Bibliographically approved
6. Relation between Microstructural Evolution, Order- Disorder Transformation and Plastic Inhomogeneity during Deformation of Brass
Open this publication in new window or tab >>Relation between Microstructural Evolution, Order- Disorder Transformation and Plastic Inhomogeneity during Deformation of Brass
2013 (English)In: Proceeding of the 143st, TMS, San Diego, California; February 2014, 2013Conference paper, Published paper (Other academic)
Keyword
Beta Brass, Deformation, Second order phase transition
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-133417 (URN)
Conference
143st, TMS, San Diego, California; February 2014
Note

QC 20131031

Available from: 2013-10-31 Created: 2013-10-31 Last updated: 2013-11-04Bibliographically approved

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