The influence of the fault energies on the anomalous mechanical behaviour of Ni₃Al alloys

Autor(en)

H. P. Karnthaler, E. Th Mühlbacher, C. Rentenberger

Abstrakt

Single crystals of the intermetallic, LI₂ ordered alloy Ni₇₈Al₂₂ were deformed in compression at RT and at 400°C, a temperature below and within the anomalous regime. Transmission electron microscopic (TEM) images were used to analyse the dislocation structures. At RT edge dipoles are prevailing (as in f.c.c. metals) whereas at 400°C locked screws, screw dipoles and near screw dislocations bowed out on the cube cross-slip plane (010) are predominant. Their formation is caused by a gradual transition from "normal" octahedral cross-slip to the thermal activated cube cross-slip. By comparing the experimental weak-beam TEM images with computer simulations and using anisotropic elasticity theory the complete set of fault energies was determined: γ_CSF = 235 ± 40 mJ/m², γ_APB (111)= 175 ± 15 mJ/m², γ_APB (010) = 104 ± 15 mJ/m² and γ_SISF = 6 ± 0.5 mJ/m². These values can be used to explain the shift of the anomalous increase of the yield stress to higher temperatures observed in Ni₃Al as compared with Ni₃(Al, 1 at.%Ta). The value of R = γ_APB(111)/γ_APB (010) determines the driving force for cube cross-slip (by comparing the R values of the two alloys the reverse behaviour of the shift might be expected). The value of γ_CSF is the decisive parameter, it determines the dissociation width and therefore the constriction energy of the Shockley partials of the screws. A low value of γ_CSF reduces the thermal activation necessary for the formation of KW locks and screws bowing out on (010).

Organisation(en)

Physik Nanostrukturierter Materialien

Externe Organisation(en)

Universität Wien

Journal

Acta Materialia

Band

44

Seiten

547-560

Anzahl der Seiten

14

ISSN

1359-6454

DOI

https://doi.org/10.1016/1359-6454(95)00191-3

Publikationsdatum

01-1996

Peer-reviewed

Ja

ÖFOS 2012

103018 Materialphysik, 103042 Elektronenmikroskopie

ASJC Scopus Sachgebiete

Electronic, Optical and Magnetic Materials, Ceramics and Composites, Polymers and Plastics, Metals and Alloys

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/156dbcbc-9ce6-412d-83f1-01f6731cf83b