Size effects in LiF micron-scale single crystals of low dislocation density

Document Type

Conference Proceeding

Publication Date



This study examines the deformation response of 20, 5, and 1μm 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 compressed preferentially by single slip inside a nanoindentation system. Similar to previously studied FCC-derivative metals, LiF microsamples demonstrate dramatic strengthening achieving the engineering flow stress o ≈ 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. © 2007 Materials Research Society.

Publication Title

Materials Research Society Symposium Proceedings