Theoretical Evidence for the Single-Ended-Source Controlled Yield Strengths of Micropillar FCC and BCC Metal Single Crystals

Abstract

It has been established experimentally from the beginning of 21st century that the yield strengths at room temperature of submicron sized face-centered-cubic and body-centered-cubic metallic single crystals fabricated with the focused ion beam milling process increase dramatically with decreasing specimen diameter. In this paper, the mechanisms of the strengthening have been discussed theoretically on the basis of the single-ended source activation controlled deformation in submicron sized crystals. The experimental results of the power-law dependent yield strength with the decrease of specimen size have been reproduced quantitatively for both types of metallic crystals, where in some body-centered-cubic metals we take into account the effect of the Peierls potential for the screw dislocation motion on the source activation stress.

log(τ_c/G) vs. log(D/b) plot of critical dislocation bow-out stress component for six BCC metals. The thick line is the average value for each D/b calculated theoretically on the basis of the single-ended source activation controlled deformation in submicron sized crystals. Between the thick and thin dashed lines 95% of the strength distribution is included for each D/b value in the calculated distributions.