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Spark plasma sintering and deformation behaviour of Titanium and Titanium/TiB2Spark plasma sintering and deformation behaviour of Titanium and Titanium/TiB2 composites
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
2007 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Titanium has been used as a model substance to study how it behaves in a SPS apparatus when heating rate and/or pressure were varied during the sintering and deformation process. The sintering and deformation of Ti in SPS were compared with that occurring in the conventional hot pressing (HP) in order to reveal if there are any positive effects added by the use of SPS. The ductility of Ti was explored in order to understand the sintering and deformation of (Ti) x (TiB2)1-x composites with x = 0.05, 0.1, and 0.2, respectively, expressed in mol ratio. The temperature difference (DT) between the monitored and the temperature that the samples are exposed to was evaluated.

It was noticed that Ti can be sintered at relatively low temperatures. High heating rate implied that the onset temperatures of the sintering and deformation processes decreased. Increasing pressure did not affect the onset temperature but revealed that the deformation of Ti is different if the experiments are conducted within the stability region of the a -phase region of Ti or if the deformation takes place in a temperature region that covers both a-and b-phase areas, i. e. the use of high pressures implied a one step deformation process while the use of low implied that the main part of the deformation took place in the b-phase region.

(Ti) x (TiB2)1-x composites were prepared to full densities at 1500 °C using a holding time of 3 min and pressure of 50 MPa. During the SPS sintering the composite with x= 0.2 revealed the presence of TiB due to the reaction Ti + TiB 2 -> 2TiB while the composites with low x values did not show any formation of TiB. The formation of TiB impaired the mechanical properties. The deformation of composites was very difficult. Their deformability increased with increasing x and temperature as well as pressure. During the deformations of pre-sintered samples TiB was formed in all of the composites.

Place, publisher, year, edition, pages
2007. , 33 p.
Research subject
Materials Science
Identifiers
URN: urn:nbn:se:su:diva-26122OAI: oai:DiVA.org:su-26122DiVA: diva2:202507
Presentation
(English)
Opponent
Supervisors
Available from: 2010-01-20 Created: 2009-03-10 Last updated: 2010-04-27Bibliographically approved
List of papers
1. Spark plasma sintering and deformation of Ti-TiB2 composites.
Open this publication in new window or tab >>Spark plasma sintering and deformation of Ti-TiB2 composites.
2008 (English)In: Materials Science & Engineering, A: Structural Materials: Properties, Microstructure and Processing, ISSN 0921-5093, Vol. 1-2, no A475, 101-104 p.Article in journal (Refereed) Published
Abstract [en]

Spark plasma sintering (SPS) was used to investigate the densification and deformation behaviour of Ti–TiB2 composites. Fully densified samples were prepared with Ti addition larger than 5%. The prepared composites can be deformed under compression at 1700 °C to achieve a strain of 50% without cracking. At lower temperatures, cracks were initiated due to low ductility of TiB2 and low content of Ti. During the sintering and deformation, TiB is formed via a reaction between Ti and TiB2. To elucidate the formation mechanism of TiB in the SPS process, reactive sintering of TiB using element precursors was also performed. Fully dense samples were prepared but it was not possible to prepare pure uniphase TiB. The reactive sintering resulted in the formation of TiB and TiB2 mixtures at low temperatures and a mixture of TiB2 and Ti3B4 at high temperature

Place, publisher, year, edition, pages
Elsevier, 2008
Keyword
Spark plasma sintering; Titanium; Titanium diboride; Grain growth; Reactive sintering
National Category
Environmental Sciences
Identifiers
urn:nbn:se:su:diva-17243 (URN)10.1016/j.msea.2007.01.161 (DOI)000253693100020 ()
Available from: 2009-01-10 Created: 2009-01-10 Last updated: 2010-04-26Bibliographically approved
2. Fast densification and deformation of titanium powder
Open this publication in new window or tab >>Fast densification and deformation of titanium powder
2005 (English)In: Powder Metallurgy, ISSN 0032-5899, Vol. 48, no 3, 231-236 p.Article in journal (Refereed) Published
Abstract [en]

 A coarse titanium powder containing 0.2 wt-% oxygen with an average particle size of 45 micrometers was rapidly densified using the spark plasma sintering (SPS) technique. The fully consolidated specimens were also deformed in compression in the SPS unit and in a conventional hot pressing (HP) furnace. The densification and deformation behaviours were investigated by microstructural observation and examining the shrinkage and shrinkage rate recorded in real time. The efforts were focused on clarifying to what extent the possible spark discharging and intensive Joule heating at the particle contact points contribute to the densification, and what effect if any the pulsed electrical heating has on the densification. The results showed that what contributed to the densification were neither spark discharging nor anisotropic heating, but the particle deformation. Deformation occurs throughout the entire particle both in SPS and HP conditions, with a higher strain rate under SPS condition especially in the a phase region.

Place, publisher, year, edition, pages
Maney Publishing, 2005
Keyword
Spark Plasma Sintering, Electrical Field, Densification, Deformation, Titanium
National Category
Environmental Sciences
Identifiers
urn:nbn:se:su:diva-26119 (URN)10.1179/174329005X71939 (DOI)
Available from: 2009-03-10 Created: 2009-03-10 Last updated: 2010-04-27Bibliographically approved

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