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The influence of Si on the microstructure and sintering behavior of ultrafine WC

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Title: The influence of Si on the microstructure and sintering behavior of ultrafine WC
Authors: Kumar, A. K. Nanda Browse this author
Watabe, Masaaki Browse this author
Kurokawa, Kazuya Browse this author
Keywords: nanoscale WC-Si
abnormal grain growth
spark plasma sintering
faceting
platelet
Issue Date: 10-Jul-2012
Publisher: Taylor & Francis
Journal Title: Philosophical Magazine
Volume: 92
Issue: 32
Start Page: 3950
End Page: 3967
Publisher DOI: 10.1080/14786435.2012.700127
Abstract: The microstructure of sintered nano scale tungsten carbide powders with 1wt. % Si addition was found to be populated by an abnormally large number of elongated grains. Interrupted sintering experiments were conducted to clarify the origins of the excessive abnormal grain growth seen in the microstructure. It was observed that rapid coarsening occurred at high temperatures owing to the formation of a liquid phase. However, the grain shape evolution during this coarsening period was found to be a consequence of excessive stacking faults and micro twins on the basal planes probably generated by reaction of WC with Si. Analyses of the microstructures and the isothermal and non isothermal coarsening behaviors suggested that the platelet morphology evolved by defect-assisted nucleation and growth on faceted grains. Based on experimental evidence from samples interrupted at low temperatures and crystal growth theories, we discuss the possible mechanisms that eventually led to the rampant platelet-type morphology. Further, the influence of such rapid grain growth on the shrinkage rate during sintering is also discussed. In comparison with the cyclic coarsening-densification process of sintering in pure nano scale WC, the addition of Si leads to only two distinct sintering stages: either densification dominated or coarsening dominated. Concurrent densification and coarsening cannot be sustained particularly in the presence of a liquid phase that significantly enhances coarsening.
Rights: This is an Author's Accepted Manuscript of an article published in Philosophical Magazine, Volume 92, Issue 32, pages 3950-3967, 2012, © 2012 Taylor & Francis, available online at: http://www.tandfonline.com/10.1080/14786435.2012.700127
Type: article (author version)
URI: http://hdl.handle.net/2115/52953
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: A. K. Nanda Kumar

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