Pre-straining effects on the power-law scaling of size-dependent strengthening in Ni single crystals

Jaafar A. El-Awady, Michael D. Uchic, Paul A. Shade, Sang-Lan Kim, Satish I. Rao, Dennis M. Dimiduk, Christopher Woodward

Volume 68, Issues 3–4, February 2013, Pages 207–210

We report experimental and three-dimensional discrete dislocation dynamics measurements to characterize the effect of high starting dislocation density on size-affected flow. Microcrystals were focused ion beam milled into a pre-strained bulk Ni single crystal to obtain dense heterogeneous dislocation cell structure. The strength-scaling exponent is shown to decrease considerably with increasing dislocation density. Cutting the pre-existing forest during microcrystal fabrication can lead to alternate pathways for the advancing slipped areas to defeat the forest, resulting in a lower strength than the pre-strained bulk crystal. 

http://dx.doi.org/10.1016/j.scriptamat.2012.10.035