Metallurgical and Materials Transactions A

, Volume 25, Issue 4, pp 677–685

Nanocrystalline iron sintering behavior and microstructural development

  • D. L. Bourell
  • W. A. Kaysser
Transformations

Abstract

Nanocrystalline (20 nm) iron powder was closed-die sintered in a hydrogen atmosphere at a stress of 10.1 MPa and at temperatures between 670 and 1270 K. The maximum densification rate was approximately 6 × 10−4 s−1. Density greater than 90 pct was obtained at sintering temperatures greater than 990 K. Densification was marked microstructurally by local gradients which appeared after initial cold compaction. Oxygen content in the starting powder was high but was effectively a monolayer of surface adsorbed oxygen. Despite the reducing sintering atmosphere, oxide was present in dense specimens as a fine dispersion of order 0.1 to 1µm. The extent of oxide formation can be controlled by closed-die sintering to a stable structure of interconnected porosity followed by open-die resintering in the reducing atmosphere. Final grain size in material sintered 1 hour at 1080 K was generally less than 200 nm, although scattered coarsening to approximately 5 µm was observed.

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Copyright information

© The Minerals, Metals and Materials Society, and ASM International 1994

Authors and Affiliations

  • D. L. Bourell
    • 1
  • W. A. Kaysser
    • 2
  1. 1.Center for Materials Science and EngineeringThe University of Texas at AustinAustinTX
  2. 2.DLR Institute for Materials ResearchCologneGermany

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