Dislocation Densities in Deformed Cu-Al Single Crystals

Abstract

Dislocation densities in deformed Cu-2.5 at%Al, Cu-5.0 at%Al, Cu-10 at%Al and Cu-15 at%Al were measured by counting etch pits on the {111} plane. The relation between the dislocation density and some of the physical properties were studied.
The results obtained were as follows:
(1) The dislocation density increased proportionally with strain in stage I. In stage II the same relation was obtained, though the increasing rate of dislocation density was larger.
(2) The dislocation density on the (111) plane was higher than that on the (11\bar1). Dislocation densities on these two planes became similar with increasing strain. In Cu-2.5 at%Al dislocation density on the two planes were of the same order at the beginning of the stage II, but in Cu-15 at%Al there was a larger difference in dislocation density even at the largest stress measured.
(3) In stage I the dislocation density was proportional to stress. In stage II the square root of dislocation density was proportional to stress. This relation holds not only for the primary dislocation density but also for the secondary dislocation density.
(4) In the equation τ=αGbN^1⁄2, α∼0.65 was obtained for all the Al concentrations examined.
(5) The rate of strain hardening in stage I was found to be proportional to the increasing rate of dislocation density for all the specimens.