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Fließspannungsverhalten ultrafeinkörniger Aluminiumwerkstoffe unter besonderer Berücksichtigung der Dehnrate

Authors
Publisher
Universitätsbibliothek Chemnitz
Publication Date
Keywords
  • Ecae
  • Ecap
  • Equal-Channel Angular Extrusion
  • Equal-Channel Angular Pressing
  • Thermische Aktivierung
  • Verfestigungsrate
  • Ddc:620
  • Dehngeschwindigkeit
  • Dehnungsmessstreifen
  • Druckversuch
  • Formänderungsgeschwindigkeit
  • Nanostrukturiertes Material
  • Ultrafeinkorn
  • Umformen
  • Umformwerkzeug
  • Verfestigung
  • Verfestigungskurve
  • Versetzungsbewegung
  • Zugversuch

Abstract

Because of their exceptional properties ultrafine-grained materials, processed from conventional polycrystalline materials by severe plastic deformation, have gained increasing scientific and industrial interest during the last two decades. Based on the concept of work-hardening for f.c.c. metals the commercially pure aluminium AA1070 (Al99,7 – soft annealed) and the aluminium alloy AA6060 (AlMgSi – peak aged) were investigated. ECAP was used to introduce very high strains and an ultrafine-grained microstructure with grain sizes down to 660 nm and 310 nm. Subsequently compression and tensile tests were performed in a wide range of strain rates over seven decades up to the range of impact loading of 10^3 s^-1. The results indicate that strain path and the corresponding dislocation structure is important for the post-ECAP yielding and the following hardening response. Furthermore the precipitates of the AA6060 clearly constrain the interactions of dislocations in work-hardening stage III – causing lower strain rate sensitivity. If compared to the AA1070 they avoid hardening in stage V where an additional rate and temperature depending effect contributes – caused by the interaction of deformation induced vacancies and dislocations. The results indicate that the strain-hardening behavior can be described by thermal activated mechanisms.

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