Effect of cold-work on the Hall–Petch breakdown in copper based micro-components

[Display omitted] •The interactive grain/subgrain size effects in micro-parts’ mechanical properties.•A low value of t/d will not always cause size effect.•Substructural dimensions must be considered in for Hall–Petch modifications. Effects of substructural dimensions on the mechanical properties of...

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Bibliographic Details
Published in:Mechanics of materials 2015-01, Vol.80, p.124-135
Main Authors: Ghassemali, Ehsan, Tan, Ming-Jen, Wah, Chua Beng, Lim, S.C.V., Jarfors, Anders E.W.
Format: Article
Language:English
Subjects:
ANNEALING PROCESSES
Breakdown
Copper
Dislocation cells
Forging
Grain size
GRAIN SIZE AND SHAPE
Grains
MECHANICAL PROPERTIES
Microforming
Microstructure
PROPERTIES
Size effect
Subgrain
SUBSTRUCTURE
Substructures
YIELD STRENGTH
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Summary:[Display omitted] •The interactive grain/subgrain size effects in micro-parts’ mechanical properties.•A low value of t/d will not always cause size effect.•Substructural dimensions must be considered in for Hall–Petch modifications. Effects of substructural dimensions on the mechanical properties of micro-pins produced by an open-die micro-extrusion/forging process were studied. Micro-pins of diameter 0.3mm were manufactured from copper strips, having different initial grain sizes. Micro-compression tests on the micro-pins revealed no significant size effect, even if the number of grains over the diameter of the micro-pins falls below its critical value. However, relaxation of the as-formed substructure using recovery annealing led to a surprising drop in the flow stress of the micro-pins. This was explained and attributed to the number of subgrains over the diameter of the micro-pins, showing the important role of subgrains rather than grains in determining the mechanical properties.
ISSN:0167-6636
1872-7743
1872-7743
DOI:10.1016/j.mechmat.2014.10.003