| 1. |
- Bernard-Granger, Guillaume, et al.
(author)
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Phenomenological analysis of densification mechanism during spark plasma sintering of MgAl2O4
- 2009
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In: Journal of Materials Research. - 0884-2914 .- 2044-5326. ; 24:6, s. 2011-2020
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Journal article (peer-reviewed)abstract
- Spark plasma sintering (SPS) of MgAl2O4 powder was investigated at temperatures between 1200 and 1300 degrees C. A significant grain growth was observed during densification. The densification rate always exhibits at least one strong minimum, and resumes after an incubation period. Transmission electron microscopy investigations performed on sintered samples never revealed extensive dislocation activity in the elemental grains. The densification mechanism involved during SPS was determined by anisothermal (investigation of the heating stage of a SPS run) and isothermal methods (investigation at given soak temperatures). Grain-boundary sliding, accommodated by an in-series {interface-reaction/lattice diffusion of the O-2(-) anions} mechanism controlled by the interface-reaction step, governs densification. The zero-densification-rate period, detected for all soak temperatures, arise from the difficulty of annealing vacancies, necessary for the densification to proceed. The detection of atomic ledges at grain boundaries and the modification of the stoichiometry of spinel during SPS could be related to the difficulty to anneal vacancies at temperature soaks.
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| 2. |
- Eriksson, Mirva, et al.
(author)
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Fast densification and deformation of titanium powder
- 2005
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In: Powder Metallurgy. - : Maney Publishing. - 0032-5899. ; 48:3, s. 231-236
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Journal article (peer-reviewed)abstract
- 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.
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| 3. |
- Eriksson, Mirva, et al.
(author)
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Spark plasma sintering and deformation of Ti-TiB2 composites.
- 2008
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In: Materials Science & Engineering, A: Structural Materials: Properties, Microstructure and Processing. - : Elsevier. - 0921-5093. ; 1-2:A475, s. 101-104
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Journal article (peer-reviewed)abstract
- 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
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| 4. |
- Bernard-Granger, G., et al.
(author)
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Influence of graphite contamination on the optical properties of transparent spinel obtained by spark plasma sintering
- 2009
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In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 60:3, s. 164-167
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Journal article (peer-reviewed)abstract
- The optical properties of transparent spinel sintered by spark plasma sintering have been investigated for incident electromagnetic radiations with wavelengths in the range 0.2-2 mu m. It is shown that residual porosities and second-phase graphite particles have a strong influence on the in-line transmittance. Because of the graphite particles, the in-line transmittance measured does not approach that of monocrystalline spinel for wavelengths above 1 mu m.
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