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Open AccessArticle

Nanoscale Origins of the Size Effect in the Compression Response of Single Crystal Ni-Base Superalloy Micro-Pillars

Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK
Department of Engineering Mechanics, Xi’an Jiaotong University, Xi’an 710049, China
Department of Mechanical Engineering Sciences, University of Surrey, Guildford GU2 7XH, UK
Author to whom correspondence should be addressed.
Materials 2018, 11(4), 561;
Received: 25 March 2018 / Revised: 3 April 2018 / Accepted: 4 April 2018 / Published: 5 April 2018
(This article belongs to the Special Issue ICKEM2018 - Hierarchically Structured Materials (HSM))
Nickel superalloys play a pivotal role in enabling power-generation devices on land, sea, and in the air. They derive their strength from coherent cuboidal precipitates of the ordered γ’ phase that is different from the γ matrix in composition, structure and properties. In order to reveal the correlation between elemental distribution, dislocation glide and the plastic deformation of micro- and nano-sized volumes of a nickel superalloy, a combined in situ nanoindentation compression study was carried out with a scanning electron microscope (SEM) on micro- and nano-pillars fabricated by focused ion beam (FIB) milling of Ni-base superalloy CMSX4. The observed mechanical response (hardening followed by softening) was correlated with the progression of crystal slip that was revealed using FIB nano-tomography and energy-dispersive spectroscopy (EDS) elemental mapping. A hypothesis was put forward that the dependence of material strength on the size of the sample (micropillar diameter) is correlated with the characteristic dimension of the structural units (γ’ precipitates). By proposing two new dislocation-based models, the results were found to be described well by a new parameter-free Hall–Petch equation. View Full-Text
Keywords: micropillar; nanoindentation; dislocation; superalloys micropillar; nanoindentation; dislocation; superalloys
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MDPI and ACS Style

Ying, S.; Ma, L.; Sui, T.; Papadaki, C.; Salvati, E.; Romano Brandt, L.; Zhang, H.; Korsunsky, A.M. Nanoscale Origins of the Size Effect in the Compression Response of Single Crystal Ni-Base Superalloy Micro-Pillars. Materials 2018, 11, 561.

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