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Size Effects in LiF Micron-Scale Single Crystals of Low Dislocation Density

Published online by Cambridge University Press:  26 July 2012

Edward M. Nadgorny ,
Dennis M. Dimiduk  and
Michael D. Uchic
Edward M. Nadgorny
Affiliation:
nadgorny@mtu.edu, Michigan Technological University, Physics, 1400 Townsend Dr, Houghton, MI, 49931-1295, United States
Dennis M. Dimiduk
Affiliation:
Dennis.Dimiduk@wpafb.af.mil, Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB, OH, 45433-7817, United States
Michael D. Uchic
Affiliation:
Michael.Uchic@wpafb.af.mil, Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB, OH, 45433-7817, United States
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Abstract

This study examines the deformation response of 20, 5, and 1 micron diameter samples fabricated by FIB-milling from bulk ultrapure LiF single crystals. The bulk crystals have a very low initial dislocation density as revealed by an etch-pit technique. Two types of <001> microsamples were deformed preferentially by single slip when compressed inside a nanoindentation system. Similar to previously studied FCC-derivative metals, LiF microsamples demonstrate dramatic strengthening achieving the engineering flow stress σ ≈ 650 MPa in 1-μm samples. The stress-diameter dependence obeys a power law, σ ∼ D−m, where m ≈ 0.8. Stochastic variation of flow stress, fast intermittent deformation events (“avalanches”) and highly localized slip bands after avalanches - all characteristic of size effects in metals, are also observed in LiF. Possible dislocation mechanisms of the observed size effects are discussed.

Keywords

dislocationsstress/strain relationshipstrength
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 976: Symposium EE – Size Effects in the Deformation of Materials – Experiments and Modeling , 2006 , 0976-EE06-24
Copyright
Copyright © Materials Research Society 2007

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