Advanced Characterization of Twins Using Automated Electron Backscatter Diffraction

Abstract

Abstract. This paper describes results obtained using an automated, crystallographically-based technique for twin identification. The technique is based on the automated collection of spatially specific orientation measurements by electron backscatter diffraction (EBSD) in the scanning electron microscope (SEM). The key features of the analysis are identification of potential twin boundaries by their misorientation character, identification of the distinct boundary planes among the symmetrically equivalent candidates, and validation of these boundaries through comparison with the boundary and twin plane traces in the sample cross section. Results on the application of this technique to deformation twins in zirconium are analyzed for the effect of twin type and amount and sense of uniaxial deformation. The accumulation of strain tends to increase the misorientation deviation at least to the degree of the trace deviation compared with recrystallization twins in nickel. In addition to the results on characterizing the twin character, results on extending the twin analysis to automated identification of parent and daughter material for structures exhibiting twin deformation are reported as well.

Deformation twinning in explosively-driven tantalum

“…Mason et al [19] and Wright et al [20] developed a protocol for the identification of twin boundaries, the discrimination of twinned from untwinned material and the estimation of area fraction of each twin type from EBSD data. Twin boundaries have specific crystallographic properties that enable their analysis from 2-dimensional sections beyond that for general high-angle boundaries (GHABs).…”

A semiautomated electron backscatter diffraction technique for extracting reliable twin statistics

“…The most correct twin data would be achieved by using all three twin criteria in sequence. However, Wright et al [26] have reported that difficulties exist with the grain boundary trace criterion, so in this study, only the misorientation and K 1 plane coincidence criteria were tested in combination with manual parent selection. Table III shows the results of these tests compared with the baseline analysis.…”

“…The line of intersection of the predicted twin plane and the sample section plane should be parallel to the experimental grain boundary. The details of this comparison are discussed by Wright et al [26] This third criterion is called the twin boundary trace comparison. Mason et al [23] provided explicit examples of these three criteria with corresponding advantages and limitations.…”

“…The deficiency in this analysis arises from the use of a known, "uniform" macroscopic stress instead of the actual, unknown local stress field to calculate the resolved shear stress. Another scheme using a "majority rule" selection criterion [26] has been proposed that assumes that the area of twinned material will be less than one-half of the original volume; thus, the dominant orientation within a grain is assumed to be the parent orientation. This approach has the advantage that the twin calculations can be completely automated in a straightforward manner.…”

“…[22] Analysis of these data sets can enable the quantification of twinning with greater accuracy than is available through optical microscopy [23][24][25][26] and yield better statistical data than TEM. To expand on this capability, a semiautomated analysis technique was developed that first identifies and verifies possible twin boundaries in a deformed microstructure using the proposed criterion [23] and then associates these twin boundaries with manually preselected parent orientations in each METALLURGICAL …”