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In-situ tensile testing of single-crystal molybdenum-alloy fibers with various dislocation densities in a scanning electron microscope

Published online by Cambridge University Press:  23 September 2011

Kurt E. Johanns ,
Andreas Sedlmayr ,
P. Sudharshan Phani ,
Reiner Mönig ,
Oliver Kraft ,
Easo P. George  and
George M. Pharr
Kurt E. Johanns
Affiliation:
Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996
Andreas Sedlmayr
Affiliation:
Karlsruhe Institute of Technology, Institute for Materials Research II (IMF II), 76021 Karlsruhe, Germany
P. Sudharshan Phani
Affiliation:
Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996
Reiner Mönig
Affiliation:
Karlsruhe Institute of Technology, Institute for Materials Research II (IMF II), 76021 Karlsruhe, Germany
Oliver Kraft
Affiliation:
Karlsruhe Institute of Technology, Institute for Materials Research II (IMF II), 76021 Karlsruhe, Germany
Easo P. George
Affiliation:
Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996; and Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
George M. Pharr*
Affiliation:
Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996; and Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
*
a)Address all correspondence to this author. e-mail: pharr@utk.edu
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Abstract

In-situ tensile tests have been performed in a dual beam focused ion beam and scanning electron microscope on as-grown and prestrained single-crystal molybdenum-alloy (Mo-alloy) fibers. The fibers had approximately square cross sections with submicron edge lengths and gauge lengths in the range of 9–41 μm. In contrast to previously observed yield strengths near the theoretical strength of 10 GPa in compression tests of ∼1–3-μm long pillars made from similar Mo-alloy single crystals, a wide scatter of yield strengths between 1 and 10 GPa was observed in the as-grown fibers tested in tension. Deformation was dominated by inhomogeneous plastic events, sometimes including the formation of Lüders bands. In contrast, highly prestrained fibers exhibited stable plastic flow, significantly lower yield strengths of ∼1 GPa, and stress–strain behavior very similar to that in compression. A simple, statistical model incorporating the measured dislocation densities is developed to explain why the tension and compression results for the as-grown fibers are different.

Keywords

MoStress/strain relationshipStrength

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Type
Articles
Information
Journal of Materials Research , Volume 27 , Issue 3: Focus Issue: Advances in Mechanics of One-Dimensional Micro/Nanomaterials , 14 February 2012 , pp. 508 - 520
Copyright
Copyright © Materials Research Society 2011

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