On the CSL grain boundary distributions in polycrystals

Abstract

CSL (Coincidence Site Lattice) grain boundaries are considered to be special for polycrystals. Compared to non-special, random grain boundaries, they are believed to be low-energy, and they are observed to be resistant to intergranular fracture, creep cavitation, etc. Thus the frequencies of CSL distribution are important in Grain Boundary Characteristics Design (GBCD). In a previous paper, the influence of crystallographic texture on the frequencies of CSL grain boundary distributions in polycrystals was discussed. The authors draw the conclusion that the frequency of CSL-boundaries depends upon texture, but that this frequency is weak for textures which are not sharp. However, the potential for spatial correlations between neighboring grain orientations was not considered in this earlier work, and some recent experimental measurements in real polycrystals are in contradiction with this conclusion. Recent experimental advances make it possible to determine the crystallographic characteristics of a large number of grain boundaries in a short time. This paper illustrates two examples for fcc cubic materials: Inconel 600 alloy with a weak rolling texture, and a highly fiber-textured aluminum thin film. It is demonstrated that the occurrence of CSL boundaries is very strong in the weakly textured Inconel 600 alloy, in disagreement with theoretical estimates. Formore » the aluminum thin film, it is shown that experimental measurements and theoretical predictions are in reasonable agreement. In the next section the numerical results of theoretical and computer simulated CSL grain boundary distributions are described. Section 3 details the OIM experimental measurements. Section 4 provides a more complete discussion of the comparison between theoretical predictions and experimental measurements.« less