Experimentally determined content of a geometrically necessary dislocation boundary in copper

Abstract

Weak beam and stereo transmission electron microscopy (TEM) were used to analyze the dislocation content of a crystallographic geometrically necessary dislocation boundary (GNB) in rolled copper. The GNB is oriented close to the ( 1 ̄ 1 1) slip plane and is composed primarily of dislocations from the three highest stressed slip systems: 1 2 [ 1 ̄ 1 0](1 1 1) , 1 2 [1 0 1]( 1 ̄ 1 1) , and 1 2 [1 1 0]( 1 ̄ 1 1) . The boundary also contains a large number of dislocation nodes and reaction products (junctions) of the three primary sets including junctions of the first two sets resulting in a Lomer lock configuration 1 2 [0 1 1](1 0 0) . The dislocation configuration within the boundary appears to be a low energy structure within the confines of the system. The general boundary minimum energy solution to Frank’s formula does not agree well with the observed configuration. Solutions containing high densities of dislocations with Burgers vectors from the highest stressed slip systems give more reasonable agreement. An alternate analysis of Frank’s formula considering only slip activity on two fcc slip planes also gives reasonable results.