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Deformation behaviour of commercially pure titanium during simple hot compression
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Mechanical Metallurgy. (Mechanical Metallurgy)
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Mechanical Metallurgy. (Mechanical Metallurgy)
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Mechanical Metallurgy. (Mechanical Metallurgy)
2009 (English)In: Materials and Design, ISSN 0261-3069, Vol. 30, no 8, 3105-3111 p.Article in journal (Refereed) Published
Abstract [en]

Commercially pure titanium (CP Ti), grade II, is subjected to hot compression at temperatures ranging from 673 to 973 K with 50 K intervals and strain rates of 0.001, 0.01, 0.1 and 1/s up to 60% height reduction. By analysing work hardening rate vs. flow stress, the deformation behaviour can be divided into three groups, viz. three-stage work hardening, two-stage work hardening and flow softening. By plotting the data in a T vs. log(strain rate) diagram, the present and previous data fall into three distinct domains which can be separated by two distinct values of the Zener–Hollomon parameter. The microstructure after deformation is characterized by optical microscopy and electron back scattered diffraction. The formation of {10-11} twins is related to the Zener–Hollomon parameter. Geometric dynamic recrystallization seems most appropriate when describing the grain refinement process of CP Ti during hot compression.

Place, publisher, year, edition, pages
2009. Vol. 30, no 8, 3105-3111 p.
Keyword [en]
Commercially pure titanium, Zener–Hollomon parameter, High angle grain boundary
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-10413DOI: 10.1016/j.matdes.2008.12.002ISI: 000267746800034Scopus ID: 2-s2.0-67349114922OAI: oai:DiVA.org:kth-10413DiVA: diva2:216813
Note
QC 20100819Available from: 2009-05-18 Created: 2009-05-12 Last updated: 2010-12-07Bibliographically approved
In thesis
1. Deformation Behaviour, Microstructure and Texture Evolution of CP Ti Deformed at Elevated Temperatures
Open this publication in new window or tab >>Deformation Behaviour, Microstructure and Texture Evolution of CP Ti Deformed at Elevated Temperatures
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the present work, deformation behavior, texture and microstructure evolution of commercially pure titanium (CP Ti) are investigated by electron backscattered diffraction (EBSD) after compression tests at elevated temperatures. By analysing work hardening rate vs. flow stress, the deformation behaviour can be divided into three groups, viz. three-stage work hardening, two-stage work hardening and flow softening. A new deformation condition map is presented, dividing the deformation behavior of CP Ti into three distinct zones which can be separated by two distinct values of the Zener-Hollomon parameter. The deformed microstructures reveal that dynamic recovery is the dominant deformation mechanism for CP Ti during hot working. It is the first time that the Schmid factor and pole figures are used to analyse how the individual slip systems activate and how their activities evolve under various deformation conditions. Two constitutive equations are proposed in this work, one is for single peak dynamic recrystallization (DRX), the other is specially for CP Ti deformed during hot working. After the hot compression tests, some stress-strain curves show a single peak, leading to the motivation of setting up a DRX model. However, the examinations of EBSD maps and metallography evidently show that the deformation mechanism is dynamic recovery rather than DRX. Then, the second model is set up. The influence of the deformation conditions on grain size, texture and deformation twinning is systematically investigated. The results show that {10-12} twinning only occurs at the early stage of deformation. As the strain increases, the {10-12} twinning is suppressed while {10- 11} twinning appears. Three peaks are found in the misorientation frequency-distribution corresponding to basal fiber texture, {10-11} and {10-12} twinning, respectively. A logZ-value of 13 is found to be critical for both the onset of {10-11} compressive twinning and the break point for the subgrain size. The presence of {10-11} twinning is the key factor for effectively reducing the deformed grain size. The percentage of low angle grain boundaries decreases with increasing Z-parameter, falling into a region separated by two parallel lines with a common slope and 10% displacement. After deformation, three texture components can be found, one close to the compression direction, CD, one 10~30° to CD and another 45° to CD.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. iv, ii, 57 p.
Keyword
Commercially pure titanium; Zener–Hollomon parameter; Dynamic recovery; Dynamic recrystallization; Recrystallized volume fraction; Grain size; Flow stress; Constitutive equation; Texture; High angle grain boundary; Low angle grain boundary; Deformation twinning; Schmid factor; Misorientation; Hot compression; Slip system; Subgrain; EBSD
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-10404 (URN)978-91-7415-305-7 (ISBN)
Public defence
2009-06-04, B2, KTH, Brinellvägen 23, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100819Available from: 2009-05-18 Created: 2009-05-11 Last updated: 2010-08-19Bibliographically approved

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