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Article: A TEM investigation on indentation plastic zones in Ni3Al(Cr,B) single crystals

TitleA TEM investigation on indentation plastic zones in Ni3Al(Cr,B) single crystals
Authors
KeywordsMechanical Properties
Nanoindentation
Single Crystal
Yield Phenomena
Issue Date2002
PublisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/actamat
Citation
Acta Materialia, 2002, v. 50 n. 10, p. 2677-2691 How to Cite?
AbstractNanoindentation has been carried out on (111) single crystals of Ni3Al with the maximum applied load ranging from 800 to 8000 μN. The indentation plasticity fields are found to consist of two regions, namely, a core with a very high dislocation density and a surrounding region where the dislocation density is much lower. In the zone with lower dislocation density, individual dislocations were discernible, and three sets of dislocations, with Burgers vector of the 〈11̄0〉 type and parallel to the sample surface, were identified in all specimens. The dislocation segments were curvy at small loads but long and straight screw dislocations appeared at large loads. Measurements of the radii of the plasticity zones from TEM images indicate that the core and the surrounding low dislocation density zone did not evolve in a self-similar manner with increasing load. From the dislocation structure observed just after the pop-in in the load-displacement curve, the strain rate in the indent core during pop-in is estimated to be about 170 s-1. The nominal hardness calculated using the Oliver-Pharr scheme exhibits a sharp and negative dependence with respect to load, with the hardness dropping from ∼ 12 GPa at 800 μN to about 6 GPa at 8000 μN. The value of P/πc2, where P is the load and c the radius of the surrounding dislocation zone, is however fairly constant with respect to load, with a variation of only about 10% in the same load range. The yield stress Y calculated from the equation Y = 1.5P/πc2 is about 356±32 MPa. These results suggest that, while nanohardness can still be expected to depend critically on the yield stress, there is an additional functional relationship that causes the hardness to vary with the indent size in the submicron regime. © 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
Persistent Identifierhttp://hdl.handle.net/10722/156647
ISSN
2015 Impact Factor: 5.058
2015 SCImago Journal Rankings: 3.683
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorChiu, YLen_US
dc.contributor.authorNgan, AHWen_US
dc.date.accessioned2012-08-08T08:43:22Z-
dc.date.available2012-08-08T08:43:22Z-
dc.date.issued2002en_US
dc.identifier.citationActa Materialia, 2002, v. 50 n. 10, p. 2677-2691en_US
dc.identifier.issn1359-6454en_US
dc.identifier.urihttp://hdl.handle.net/10722/156647-
dc.description.abstractNanoindentation has been carried out on (111) single crystals of Ni3Al with the maximum applied load ranging from 800 to 8000 μN. The indentation plasticity fields are found to consist of two regions, namely, a core with a very high dislocation density and a surrounding region where the dislocation density is much lower. In the zone with lower dislocation density, individual dislocations were discernible, and three sets of dislocations, with Burgers vector of the 〈11̄0〉 type and parallel to the sample surface, were identified in all specimens. The dislocation segments were curvy at small loads but long and straight screw dislocations appeared at large loads. Measurements of the radii of the plasticity zones from TEM images indicate that the core and the surrounding low dislocation density zone did not evolve in a self-similar manner with increasing load. From the dislocation structure observed just after the pop-in in the load-displacement curve, the strain rate in the indent core during pop-in is estimated to be about 170 s-1. The nominal hardness calculated using the Oliver-Pharr scheme exhibits a sharp and negative dependence with respect to load, with the hardness dropping from ∼ 12 GPa at 800 μN to about 6 GPa at 8000 μN. The value of P/πc2, where P is the load and c the radius of the surrounding dislocation zone, is however fairly constant with respect to load, with a variation of only about 10% in the same load range. The yield stress Y calculated from the equation Y = 1.5P/πc2 is about 356±32 MPa. These results suggest that, while nanohardness can still be expected to depend critically on the yield stress, there is an additional functional relationship that causes the hardness to vary with the indent size in the submicron regime. © 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.en_US
dc.languageengen_US
dc.publisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/actamaten_US
dc.relation.ispartofActa Materialiaen_US
dc.subjectMechanical Propertiesen_US
dc.subjectNanoindentationen_US
dc.subjectSingle Crystalen_US
dc.subjectYield Phenomenaen_US
dc.titleA TEM investigation on indentation plastic zones in Ni3Al(Cr,B) single crystalsen_US
dc.typeArticleen_US
dc.identifier.emailNgan, AHW:hwngan@hkucc.hku.hken_US
dc.identifier.authorityNgan, AHW=rp00225en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1016/S1359-6454(02)00100-3en_US
dc.identifier.scopuseid_2-s2.0-0037067188en_US
dc.identifier.hkuros67029-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0037067188&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume50en_US
dc.identifier.issue10en_US
dc.identifier.spage2677en_US
dc.identifier.epage2691en_US
dc.identifier.isiWOS:000176432500016-
dc.publisher.placeUnited Kingdomen_US
dc.identifier.scopusauthoridChiu, YL=7202775086en_US
dc.identifier.scopusauthoridNgan, AHW=7006827202en_US

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