A nano-indentation study of surface plasticity in zirconium nitride

K. Wheeler, Pedro Peralta, G. W. Egeland, K. J. McClellan

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

ZrN was studied as a possible surrogate material for PuN under the Global Nuclear Energy Partnership (GNEP) and the Advanced Fuel Cycle Initiative (AFCI) programs. In particular, this work was carried out to examine the dislocation activity on the surface of monolithic ZrN and establishes the ground work of current activities to determine the variation of plasticity and fracture in specific grains of a dense sample of 1600°C sintered ZrN using nano-indentation. Samples of monolithic ZrN were carefully polished using colloidal silica suspensions (chemo-mechanical polishing) to produce a relatively strain free surface. It was found that the load-penetration curves from nano-indentation on the polished surface displayed a displacement jump of 31±3 nm at an average load of 1100±200 μN. The presence of this jump indicated a permanent indentation in the sample, whereas loads below the critical resulted in elastic behavior. This behavior has been observed in metallic materials and has been related to a sudden "avalanche" of dislocations at the point of contact between the sample surface and the indenter tip. Indentation experiments were then repeated after mechanical polishing of the surface with 1200 grit SiC paper. There was a clear increase in the surface roughness and the nano-indentation experiments indicated that the jump in the load penetration curve disappeared completely. This strongly suggests that the rough polishing produced a population of dislocations on the sample surface, which precluded the need to induce a dislocation avalanche at the indenter tip, making the jump disappear. In addition, seven grains with different crystallographic orientations were selected via Electron Backscattered Diffraction (EBSD) from a sample of ZrN sintered at 1600°C and isolated with fiducial markings using a Focused Ion Beam (FIB) to perform nano-indentation measurements as a function of orientation. Post indentation characterization and indent cross sectioning will be performed using a FIB.

Original languageEnglish (US)
Title of host publicationTMS2008 - 137th Annual Meeting and Exhibition Supplemental Proceedings
Subtitle of host publicationMaterials Processing and Properties
Pages79-84
Number of pages6
StatePublished - 2008
EventTMS 2008 Annual Meeting Supplemental: Materials Processing and Properties - New Orleans, LA, United States
Duration: Mar 9 2008Mar 13 2008

Publication series

NameTMS Annual Meeting
Volume3

Other

OtherTMS 2008 Annual Meeting Supplemental: Materials Processing and Properties
CountryUnited States
CityNew Orleans, LA
Period3/9/083/13/08

Keywords

  • Nano-indentation
  • Surface plasticity
  • Yield event
  • Zirconium nitride

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys

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