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2005 | 107 | 5 | 738-744
Article title

Defects in Ultra-Fine Grained Mg and Mg-Based Alloys Prepared by High Pressure Torsion Studied by Positron Annihilation

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EN
Abstracts
EN
Despite the favourable strength and thermal stability, a disadvantage of the Mg-based alloys consists in a low ductility. Recently it has been demonstrated that ultra fine grained metals with grain size around 100 nm can be produced by high pressure torsion. A number of ultra fine grained metals exhibit favourable mechanical properties consisting in a combination of a very high strength and a significant ductility. For this reason, it is highly interesting to examine microstructure and physical properties of ultra fine grained Mg-based light alloys. Following this purpose, microstructure investigations and defect studies of ultra fine grained pure Mg and ultra fine grained Mg-10%Gd alloy prepared by high pressure torsion were performed in the present work using positron annihilation spectroscopy combined with X-ray diffraction, TEM observations, and microhardness measurements. Positrons are trapped at dislocations in Mg and Mg-10%Gd alloy deformed by high pressure torsion. A number of dislocations increases with the radial distance r from the centre to the margin of the sample. No microvoids (small vacancy clusters) were detected. Mg-10%Gd alloy deformed by high pressure torsion exhibits a homogeneous ultra fine grained structure with a grain size around 100 nm and high dislocations density. On the other hand, pure Mg deformed by high pressure torsion exhibits a binomial type of structure which consists of "deformed regions" with ultra fine grained structure and a high dislocation density and dislocation-free "recovered regions" with large grains. It indicates a dynamic recovery of microstructure during high pressure torsion processing.
Keywords
EN
Contributors
author
  • Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, 180 00 Praha 8, Czech Republic
author
  • Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, 180 00 Praha 8, Czech Republic
author
  • Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, 180 00 Praha 8, Czech Republic
  • Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, 180 00 Praha 8, Czech Republic
author
  • Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, 180 00 Praha 8, Czech Republic
author
  • Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, 180 00 Praha 8, Czech Republic
author
  • Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, 180 00 Praha 8, Czech Republic
  • Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, Ufa 450000, Russia
author
  • Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, Ufa 450000, Russia
References
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Document Type
Publication order reference
Identifiers
YADDA identifier
bwmeta1.element.bwnjournal-article-appv107n504kz
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