The Arrangement and Distribution of Dislocations in Deformed Cu-Al Single Crystals

Abstract

The dislocation distribution and arrangement in Cu-2.5 at%Al, Cu-5 at%Al, Cu-10 at%Al and Cu-15 at%Al single crystals deformed into stage I and stage II were studied by means of the etch pit technique. Etch pit observation was made on the surface of the (1\bar1\bar1) plane, and also on the planes cut parallel to the (11\bar1) and (111) planes of each specimen. The etch pits on the (111) and (1\bar1\bar1) planes gave information on the primary (11\bar1) dislocations, and those on the (11\bar1) plane, on the secondary dislocations.
Dislocation distribution on the (111) plane of Cu-2.5 at%Al was rather regular in stage I and became long concentrated dislocation arrays in stage II. On the (11\bar1) plane a cell structure formed in stage II.
Dislocation distribution on the (11\bar1) for Cu-5 at%Al was similar to that of Cu-2.5 at%Al but the slip direction was clearer in the former. From the etch pit arrays on the (11\bar1) cut plane it became possible to distinguish the plane to which etch pit arrays belong. For Cu-10 at%Al and Cu-15 at%Al, deformation proceeded due to the widening of primary slip bands, and in the region between the slip bands no dislocation multiplications were observed. From the observation on the (11\bar1) plane it was found that dislocations which belong to the (1\bar1\bar1) plane were observed at the early stage of stage I, but the dislocations which belong to the (1\bar11) and (111) planes were multiplied where the stress-strain curve entered into the transition region from stage I to stage II. And they were observed at the restricted areas. From these experimental results it was assumed that the Lomer-Cottrell dislocations formed by interaction between (11\bar1) and (1\bar11) or (111) dislocations would be related to the transition of the stress-strain curve from stage I to stage II.