Stability of the ultrafine-grained microstructure in silver processed by ECAP and HPT

Zoltán Hegedus, J. Gubicza, Megumi Kawasaki, N. Chinh, J. Lábár, Terence G. Langdon

Research output: Contribution to journalArticle

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Abstract

The high-temperature thermal stability of the ultrafine-grained (UFG) microstructures in low stacking fault energy silver was studied by differential scanning calorimetry (DSC). The UFG microstructures were achieved by equal-channel angular pressing (ECAP) and high-pressure torsion (HPT) at room temperature (RT). The defect structure in the as-processed samples was examined by electron microscopy and X-ray line profile analysis. The stored energy calculated from the defect densities was compared to the heat released during DSC. The sum of the energies stored in grain boundaries and dislocations in the ECAP-processed samples agreed with the heat released experimentally within the experimental error. The temperature of the DSC peak maximum decreased while the released heat increased with increasing numbers of ECAP passes. The released heat for the specimen processed by one revolution of HPT was much smaller than after 4-8 passes of ECAP despite the 2 times larger dislocation density measured by X-ray line profile analysis. This dichotomy was caused by the heterogeneous sandwich-like microstructure of the HPT-processed disk: about 175 μm wide surface layers on both sides of the disk exhibited a UFG microstructure while the internal part was recrystallized, thereby yielding a relatively small released heat.

Original languageEnglish
Pages (from-to)4637-4645
Number of pages9
JournalJournal of Materials Science
Volume48
Issue number13
DOIs
Publication statusPublished - Jul 2013

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Equal channel angular pressing
Silver
Torsional stress
Microstructure
Differential scanning calorimetry
X rays
Defect structures
Defect density
Stacking faults
Dislocations (crystals)
Temperature
Electron microscopy
Grain boundaries
Thermodynamic stability
Hot Temperature
Ultrafine

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

Stability of the ultrafine-grained microstructure in silver processed by ECAP and HPT. / Hegedus, Zoltán; Gubicza, J.; Kawasaki, Megumi; Chinh, N.; Lábár, J.; Langdon, Terence G.

In: Journal of Materials Science, Vol. 48, No. 13, 07.2013, p. 4637-4645.

Research output: Contribution to journalArticle

Hegedus, Zoltán ; Gubicza, J. ; Kawasaki, Megumi ; Chinh, N. ; Lábár, J. ; Langdon, Terence G. / Stability of the ultrafine-grained microstructure in silver processed by ECAP and HPT. In: Journal of Materials Science. 2013 ; Vol. 48, No. 13. pp. 4637-4645.
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