Crack tip deformation fields in ductile single crystal media were studied experimentally. The crack, located between 2 single crystals of Al joined by a thin ductile interlayer of Sn, was introduced via selective chemical etching and could be considered to be sharp. The material around the tip was fully annealed. After mode-I loading was applied, the specimen was sectioned and the in-plane rotation field under plane strain conditions was mapped using electron back-scattering diffraction. The observations provided evidence of the main features of the deformation field, as predicted by Rice using continuum single crystal plasticity theory; especially the existence of kink shear sector boundaries which had not been clearly identified by previous studies. In order to explain the measured change in lattice rotation at the kink shear sector boundary, an alternative dislocation structure was deduced here which did not require a high concentration of dislocation sources to be distributed along the supposed kink shear sector boundary. On the basis of this, a lower bound on the dislocation density in the kink shear sector was established experimentally. The results had implications for the analytical and numerical simulation of plastic deformation in ductile single crystals; from the micron-scale to the macroscopic scale.

Crack Tip Deformation Fields in Ductile Single Crystals. J.W.Kysar, C.L.Briant: Acta Materialia, 2002, 50[9], 2367-80