Measuring the five-parameter grain-boundary distribution from observations of planar sections
- PDF / 391,194 Bytes
- 9 Pages / 607.68 x 788.88 pts Page_size
- 28 Downloads / 239 Views
12/29/04
9:46 PM
Page 1981
Measuring the Five-Parameter Grain-Boundary Distribution from Observations of Planar Sections DAVID M. SAYLOR, BASSEM S. EL-DASHER, BRENT L. ADAMS, and GREGORY S. ROHRER A stereological method is described for estimating the distribution of grain-boundary types in polycrystalline materials on the basis of observations from a single planar section. The grain-boundary distribution is expressed in terms of five macroscopically observable parameters that include: three parameters that describe the lattice misorientation across the boundary and two parameters that describe the orientation of the grain-boundary plane normal. The grain-boundary distribution is derived from measurements of grain orientations and the orientations of the lines formed where grain boundaries intersect the plane of observation. Tests of the method on simulated observations illustrate that the distribution of boundaries in a material with cubic symmetry can be reliably determined with about 10ยบ of resolution from the analysis of 5 104 or more line segments. Furthermore, grain-boundary distributions directly observed from serial sections of a SrTiO3 polycrystal are compared to those resulting from the stereological analysis of a single plane. The comparison shows that the stereological method provides a reasonable estimate of the measured distribution. The differences between the directly observed grain-boundary distribution and that derived from the stereological analysis are consistent with the results from the simulation.
I. INTRODUCTION
INTERFACES between grains or phases in threedimensional microstructures are typically observed as line segments on planar sections. While X-ray diffraction microscopy[1] and serial sectioning[2] are capable of providing complete three-dimensional characterization, each technique poses experimental challenges that have, at least until now, prevented their widespread application. In a previous article, a technique that used observations from a planar section to determine the average three-dimensional habits of fully faceted crystals embedded in a second phase was described.[3] This method, adapted from established stereological methods,[4,5] enables a statistical description of crystal habits to be determined from geometric information in conventional micrographs, along with the crystal orientation data obtained from electron back-scattered diffraction patterns (EBSPs) in a scanning electron microscope.[6] The purpose of this article is to demonstrate that the method developed for fully faceted crystals can be expanded to the more complex problem of extracting a continuous distribution of grain-boundary planes, specified by area fraction, from a single planar section through a single-phase polycrystalline material. The grain-boundary distribution, (g,n), is defined as the relative frequency of occurrence of a grain boundary DAVID M. SAYLOR, Postdoctoral Research Associate, is with the National Institute of Standards and Technology, Gaithersburg, MD 20899. Contact e-mail: david
Data Loading...
