The potential engineering of grain boundaries through thermomechanical processing

Grain boundary character distribution is a relatively new microstructural feature that describes the proportions of random and special grain boundaries as defined by the coincident site lattice model. The combination of the availability of a new experimental technique based on the automatic indexing of backscatter Kikuchi electron diffraction patterns in the scanning electron microscope (orientation imaging microscopy) and reports in the literature describing the optimization of the grain boundary character distribution through thermomechanical processing are making the potential for enhanced materials properties in commercial metals and alloys a reality. Although the effects of optimizing the grain boundary character distribution in the cost-effective improvement of properties have been documented, the potential for commercialization has limited the disclosure of processing details. In this article, two separate approaches to the optimization of the grain boundary character distribution in oxygen-free electron copper at Lawrence Livermore National Laboratory are discussed.