Weak beam and stereo transmission electron microscopy were used to analyze the dislocation content of a crystallographic geometrically necessary dislocation boundary in rolled material. The geometrically necessary dislocation boundary was oriented close to the (¯111) slip plane, and was composed mainly of dislocations from the 3 highest-stress slip systems: ½[¯110](111), ½[101](¯111) and ½[110](¯111). The boundary also contained a large number of dislocation nodes and reaction products (junctions) of the 3 primary sets; including junctions of the first 2 sets, resulting in a Lomer lock configuration: ½[011](100). The dislocation configuration within the boundary appeared to be a low-energy structure within the confines of the system. The general boundary minimum energy solution to Frank’s formula did not agree well with the observed configuration. Solutions involving high densities of dislocations, with Burgers vectors from the highest-stress slip systems, gave more reasonable agreement. An alternate analysis of Frank’s formula, which considered only slip activity on 2 face-centered cubic slip planes also gave reasonable results.

Experimentally Determined Content of a Geometrically Necessary Dislocation Boundary in Copper. R.J.McCabe, A.Misra, T.E.Mitchell: Acta Materialia, 2004, 52[3], 705-14