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

This stud), examines the size-dependent deformation response Of pure LiF single crystals using microcompression testing. Microcrystals with an < 001 > orientation and sample diameter D ranging from I to 20 mu m were fabricated by focused loll beam (FIB)-milling from bulk crystals having a low initial dislocation density. Both as-grown and gamma-irradiated crystals were examined to characterize the effect of an increased point defect density on the size-affected plastic flow response. Similar to previously Studied face-centered cubic (FCC)-derivative metals, both types of LiF microcrystals exhibit typical size-dependent plastic flow behavior: a dramatic size-dependent and statistically varying flow stress, atypically high strain hardening rates at small plastic strains. and fast intermittent strain bursts. The size-dependent strengthening, obeys a power law, sigma similar to D-'''. where m approximate to 0.8, and this rapid hardening results in enoineerincy flow stresses of 650 MPa in 1-mu m samples. The findings are evaluated against possible dislocation mechanisms that Could be responsible for the observed size effects.