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Achieving uniform microstructure and superior mechanical properties in ultrafine grained TiB2–TiSi2composites using innovative multi stage spark plasma sintering

Authors
Journal
Materials Science and Engineering A
0921-5093
Publisher
Elsevier
Publication Date
Volume
528
Issue
1
Identifiers
DOI: 10.1016/j.msea.2010.09.022
Keywords
  • Spark Plasma Sintering
  • Tib2
  • Sintering Reaction
  • Microstructure
  • Properties

Abstract

Abstract We report here the development of ultrafine grained TiB 2–TiSi 2 composites, adopting multi stage Spark Plasma Sintering (SPS) route. As opposed to the commonly used Single Stage SPS (SSS), the samples are held for a desired timescale at intermediate temperatures, before reaching the final sintering temperatures (1400 °C, 1450 °C and 1500 °C). In our innovative sintering schedule, the powder compacts are held for a comparatively lesser period at intermediate stages, in order to maintain a net holding time of 10 min altogether at different holding stages during Two Stage Sintering (TSS) and Multi Stage SPS (MSS). TSS and MSS allowed the achievement of relatively higher sinter densities with respect to SSS, when the final sintering temperature remains same. The development of finer microstructural scale, with the presence of tabular TiB 2 grains (1–1.5 μm) and TiSi 2 grains (200–300 nm) is exhibited by the ceramics sintered via TSS/MSS, with respect to those developed via SSS. MSS resulted in sintering reactions between the TiB 2 and TiSi 2 components, leading to the formation of reaction layer of Ti 5Si 3 of 50–100 nm thickness. However, such sintering reactions were relatively suppressed in the case of SSS. Finer scale microstructure allowed much higher hardness (∼27–31 GPa) to be achieved on sintering via MSS. Also, more uniform microstructural development in the case of MSS led to an improvement in three-point flexural strength (∼500 MPa), compared to composites developed via conventional hot pressing or SSS route using SPS.

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