Principles of equal-channel angular pressing as a processing tool for grain refinement

The current understanding of the fundamentals of recrystallization is summarized. This includes understanding the as-deformed state. Several aspects of recrystallization are described: nucleation and growth, the development of misorientation during deformation, continuous, dynamic, and geometric dynamic recrystallization, particle effects, and texture. This article is authored by the leading experts in these areas. The subjects are discussed individually and recommendations for further study are listed in the final section.

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Current issues in recrystallization: a review

The application of automated Electron Backscatter Diffraction (EBSD) in the scanning electron microscope, to the quantitative analysis of grain and subgrain structures is discussed and compared with conventional methods of quantitative metallography. It is shown that the technique has reached a state of maturity such that linescans and maps can routinely be obtained and analysed using commercially available equipment and that EBSD in a Field Emission SEM (FEGSEM) allows quantitative analysis of grain/subgrains as small as ∼0.2 μm. EBSD can often give more accurate measurements of grain and subgrain size than conventional imaging methods, often in comparable times. Subgrain/cell measurements may be made more easily than in the TEM although the limited angular resolution of EBSD may be problematic in some cases. Additional information available from EBSD and not from conventional microscopy, gives a new dimension to quantitative metallography. Texture and its correlation with grain or subgrain size, shape and position are readily measured. Boundary misorientations, which are readily obtainable from EBSD, enable the distribution of boundary types to be determined and CSL boundaries can be identified and measured. The spatial distribution of Stored Energy in a sample and the amount of Recrystallization may also be measured by EBSD methods.

Review Grain and subgrain characterisation by electron backscatter diffraction

A new microscopy, called orientation imaging microscopy, is described. Imaging results from precise measurements of local lattice orientation facilitated by backscattered Kikuchi diffraction. The hardware configuration of the microscope is described, and a formal description of image formation is developed. Application of the method to several cubic materials and material conditions is described. Emphasis is given to those areas of application where new insight into polycrystalline microstructures has begun to emerge.

D.G Brandon

Papers

The structure of high-angle grain boundaries