Microstructural effects and large microhardness in cobalt processed by high pressure torsion consolidation of ball milled powders

J. Sort, A. Zhilyaev, M. Zielinska, J. Nogués, S. Suriñach, J. Thibault, M. D. Baró

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97 Citations (Scopus)

Abstract

The effects of plastic deformation on Co microstructure after a high pressure torsion (HPT) process on unmilled and ball milled powders have been studied and compared to those induced simply by ball milling (BM). X-ray diffraction analyses reveal that both processing routes generate large amounts of stacking faults in Co, which result in a mixture of hcp and fcc phases. However, significant differences in the amount and type of faults accumulated are encountered between BM and HPT. The combination of both processing routes induces a heavily distorted microstructure in Co. In particular, BM + HPT brings about a drastic reduction in crystallite size. Remarkably, high values of microhardness (in excess of HV = 7.3 GPa) are obtained in foils prepared by long-term milling followed by HPT. It is proposed that, in addition to the crystallite size refinement, the large amounts of twin faults, together with the two-phase mixture, also contribute to enhance the microhardness. © 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Original languageEnglish
Pages (from-to)6385-6393
JournalActa Materialia
Volume51
DOIs
Publication statusPublished - 8 Dec 2003

Keywords

  • Mechanical milling
  • Microhardness
  • Phase transformations
  • Severe plastic deformation
  • Twinning

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