Journal
MATERIALS & DESIGN
Volume 188, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.matdes.2019.108444
Keywords
Dislocation dynamics; Size effects; Plastic fluctuations
Categories
Funding
- National Natural Science Foundation of China [51621063, 51722104, 51625103, 51790482, 51761135031, 51571157]
- National Key Research and Development Program of China [2017YFA0700701, 2017YFB0702301]
- 111 Project 2.0 of China [BP2018008]
- China Postdoctoral Science Foundation [2019M653595]
- NSFC-ANR joint project SUMMIT [51761135031, 17-CE08-0047]
- China Scholarship Council
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The continuous miniaturization of modern electromechanical systems calls for a comprehensive understanding of the mechanical properties of metallic materials specific to micrometer and sub-micrometer scales. At these scales, the nature of dislocation-mediated plasticity changes radically: sub-micrometer metallic samples exhibit high yield strengths, however accompanied by detrimental intermittent strain fluctuations endangering structural stability. In this paper, we studied the effects of plate-like theta'-Al2Cu precipitates on the strength and plastic fluctuations of Al-Cu alloys from micro-pillar compression testing. The particularity of our samples is that the plate-like precipitates have diameters commensurate with the external size of the Al-Cu micro-pillars. Our results show that these plate-like precipitates can strengthen the materials through the Orowan mechanism at large sample size. However, the breakdown of the mean-field pinning landscape weakens its suppression effect on plastic intermittency. On the other hand, the plastic intermittency can be inhibited efficiently at small sample size by using the plate-like theta'-Al2Cu precipitates penetrating the entire micro-pillar, in association with the presence of {100}-slip traces along the coherent precipitate/Al matrix interface and enhanced strain isotropy. Besides these experimental observations, we also aim to extract the laws common in different Al alloys, and address the specific plastic mechanisms for Al-Cu micro-crystals. (C) 2020 The Authors. Published by Elsevier Ltd.
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