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Monitoring of temperature profiles and surface morphologies during lasersintering of alumina ceramics
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
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(English)In: Journal of Asian Ceramic Societies, ISSN 2187-0764Article in journal (Refereed) In press
Abstract [en]

Additive manufacturing of alumina by laser is a delicate process and small changes of processing parame-ters might cause less controlled and understood consequences. The real-time monitoring of temperatureprofiles, spectrum profiles and surface morphologies were evaluated in off-axial set-up for controllingthe laser sintering of alumina ceramics. The real-time spectrometer and pyrometer were used for rapidmonitoring of the thermal stability during the laser sintering process. An active illumination imagingsystem successfully recorded the high temperature melt pool and surrounding area simultaneously. Thecaptured images also showed how the defects form and progress during the laser sintering process. Allof these real-time monitoring methods have shown a great potential for on-line quality control duringlaser sintering of ceramics.

Keyword [en]
Monitoring, Laser sintering, Ceramics, Alumina
National Category
Materials Engineering
Research subject
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-101053OAI: oai:DiVA.org:su-101053DiVA: diva2:698554
Available from: 2014-02-24 Created: 2014-02-24 Last updated: 2014-02-26Bibliographically approved
In thesis
1. Laser sintered materials with Non-equilibrium structures
Open this publication in new window or tab >>Laser sintered materials with Non-equilibrium structures
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is focused on achieving materials with non-equilibrium structures fabricated by high-energy laser sintering. The chosen precursor materials have rigid and inert structures like high-melting point ceramics or metals. It was necessary to use real-time monitoring of temperature and spectrum profiles for selecting the optimal laser parameters for the laser sintering process. This monitoring was done by an off-axial setup that also controls the surface morphologies during the laser irradiation process. The laser focal spot receives very high temperatures and subsequent extreme cooling rates within a short time period. New non-equilibrium structures will emerge ruled by kinetics, huge temperature gradients or stresses and freeze by quenching in solid state. These material structures were found to form at different length scales from nano- to macro-level, frequently by a hierarchical ordering. This opens a method to engineer materials with both hierarchical and non-equilibrium structures by a single operation in both metal and ceramics by laser sintering. In the Co-Cr-Mo alloy system, structures on three levels of lengths were observed, namely i) nano-level structures dominated by the grain boundary segregation; ii) micron-level structures characterized by the interlocked clusters of columns; and iii) macro-level structures defined by the selected laser scan patterns. The non-equilibrium structures of the Co-Cr-Mo alloy are related to mechanical, corrosion and bio-compatibility properties. In ZrO2 ceramics, the final product had a non-equilibrium nano- and micron-sized structure created by uneven absorption of laser energy and rupture. The structure inside the micron-sized grains is formed through ordered coalescence of nano-crystals. Properties of the laser sintered materials were established and related to the observed structures. The materials properties might be tailored by controlling the structures in different levels and potential applications of the new materials will be given.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry, Stockholm University, 2014. 61 p.
Keyword
Laser sintering, Materials, Non-equilibrium structures, microstructure, hierarchical structure
National Category
Materials Engineering
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-101096 (URN)978-91-7447-866-2 (ISBN)
Public defence
2014-03-31, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Accepted. Paper 3: Accepted. Paper 4: Submitted. Paper 5: Manuscript.

Available from: 2014-03-09 Created: 2014-02-25 Last updated: 2017-05-11Bibliographically approved

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