Keywords

aluminium, Geometrically necessary dislocations, lattice curvature, misorientation, strain

Abstract

This work was partially supported by MRSEC Program of the National Science Foundation (DMR-9632556), and under the auspices of the US Department of Energy and Lawrence Livermore National Laboratory under contract W-7405- Eng-48. S. Sun gratefully acknowledges the comments of Professor E. T. Onat, Professor B. T. Chu and Professor W. Tong of the Mechanical Engineering Department at Yale University, and their valuable guidance in the process of completing this project as a doctoral dissertation. The assistance of B. El-Dasher of Carnegie-Mellon University is also gratefully acknowledged. Reported here is a study of the pattern of lattice curvature near the interface of deformed high-purity aluminium (99.9999%) bicrystals of specified crystallographic character (large-angle random). Curvature data are obtained from electron back-scattering diffraction pattern observations using orientation imaging microscopy. The concept of geometrically necessary dislocations (GNDs) is used as the central tool in the description of the observations. The samples studied were channel-die compressed perpendicular to the interface to plastic strain levels of 0.1 and 0.3. At a strain level of 0.1 the primary observation is the development of a pile-up of GNDs (i.e. lattice curvature) near the interface. At the higher strain level of 0.3, however, a dramatic change in the distribution is observed. The nature of this change suggests that the interface has absorbed (or emitted) some components of the nearby GND field, with an accompanying change in the local character of the interface towards a broader dispersion of misorientation character.

Original Publication Citation

Philosophical Magazine A, 2, Vol. 8, No. 1, 9-25