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Microcantilever bending experiments in NiAl – Evaluation, size effects, and crack tip plasticity

Published online by Cambridge University Press:  26 September 2014

Johannes Ast ,
Thomas Przybilla ,
Verena Maier ,
Karsten Durst  and
Mathias Göken
Johannes Ast*
Affiliation:
Department of Material Science and Engineering, University of Erlangen-Nürnberg, Institute I, Erlangen 91058, Germany
Thomas Przybilla
Affiliation:
Department of Material Science and Engineering, University of Erlangen-Nürnberg, Institute VII, Erlangen 91058, Germany
Verena Maier
Affiliation:
Department of Materials Physics, University of Leoben, Leoben 8700, Austria; and Department of Material Science and Engineering, University of Erlangen-Nürnberg, Institute I, Erlangen 91058, Germany
Karsten Durst
Affiliation:
Department of Physical Metallurgy, Technical University of Darmstadt, Darmstadt 64287, Germany
Mathias Göken
Affiliation:
Department of Material Science and Engineering, University of Erlangen-Nürnberg, Institute I, Erlangen 91058, Germany
*
a)Address all correspondence to this author. e-mail: johannes.ast@fau.de
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Abstract

For a better understanding of the local fracture behavior of semi-brittle materials, we carried out bending experiments on notched microcantilevers of varying sizes in the micrometer range using NiAl single crystals. Smaller and larger beams were milled with a focused ion beam in the so-called “soft” <110> and “hard” <100> orientation and were tested in situ in a scanning electron microscope and ex situ with a nanoindenter, respectively. The measurements were evaluated using both linear-elastic fracture mechanics and elastic–plastic fracture mechanics. The results show that (i) the fracture toughness is in the same range as the macroscopically determined one which is around 3.5 MPa$\sqrt {\rm{m}}$ for the soft orientation and around 8.5 MPa$\sqrt {\rm{m}}$ for the hard orientation, that (ii) there is a strong influence of the anisotropic behavior of NiAl on the fracture toughness values, and that (iii) the J-integral technique is the most accurate quantification method.

Keywords

scanning electron microscopy (SEM)fractureion beam processing
Type
Articles
Information
Journal of Materials Research , Volume 29 , Issue 18 , 28 September 2014 , pp. 2129 - 2140
Copyright
Copyright © Materials Research Society 2014 

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