Hardening by Annealing and Softening by Deformation in Nanostructured Metals

We observe that a nanostructured metal can be hardened by annealing and softened when subsequently deformed, which is in contrast to the typical behavior of a metal. Microstructural investigation points to an effect of the structural scale on fundamental mechanisms of dislocation-dislocation and dis...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2006-04, Vol.312 (5771), p.249-251
Main Authors: Huang, Xiaoxu, Hansen, Niels, Tsuji, Nobuhiro
Format: Article
Language:English
Subjects:
Aluminum
Annealing
Cold rolling
Condensed matter: structure, mechanical and thermal properties
Deformation
Density
Ductility
Exact sciences and technology
Grain boundaries
Grain size
Materials
Mechanical and acoustical properties of condensed matter
Mechanical properties of nanoscale materials
Metals
Physics
Tensile stress
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Summary:We observe that a nanostructured metal can be hardened by annealing and softened when subsequently deformed, which is in contrast to the typical behavior of a metal. Microstructural investigation points to an effect of the structural scale on fundamental mechanisms of dislocation-dislocation and dislocation-interface reactions, such that heat treatment reduces the generation and interaction of dislocations, leading to an increase in strength and a reduction in ductility. A subsequent deformation step may restore the dislocation structure and facilitate the yielding process when the metal is stressed. As a consequence, the strength decreases and the ductility increases. These observations suggest that for materials such as the nanostructured aluminum studied here, deformation should be used as an optimizing procedure instead of annealing.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.1124268