Nanosegregation, microtexture and the control of brittle failure David B. Williams and Masashi Watanabe, Lehigh University, MET DMR Intellectual Merit Accurate determination of the grain-boundary (GB) enrichment The compositions of minor segregants to GBs that may control the brittle failure of materials can be very low and fluctuate locally. In addition, the measured segregant compositions, determined via X-ray or electron spectrometry in the analytical electron microscope, are dependent on the experimental conditions so the apparent composition may not be the true composition. We have developed methods to enhance the accuracy and precision of such minor composition values by using an advanced statistical treatment, in combination with the latest X-ray signal acquisition method. The original Ni and Mo maps from a low-alloy steel (Fig. 1) are significantly improved (Fig. 2) after the statistical treatment. Furthermore, we have developed a new quantification approach called the “  -factor method”, which can provide not only quantified compositions but also the local specimen thickness. Therefore, since we know the thickness, we can extract the GB enrichment (the number of excess atoms / unit area in the GB plane) and display this value as an image (Fig. 3). In this particular example, the GB enrichment of Ni fluctuates noticeably along the GB, but the Mo enrichment is rather homogeneous. If anything, the converse appears to be the case in the original maps ( Fig. 1). With this advance, it is now possible to visualize, directly, local differences in segregation. Ni Mo nm Ni Mo Ni Mo Fig. 1 Original composition maps (wt%) of Ni and Mo from a low-alloy steel. Fig. 2 Enhanced composition maps (wt%) of Ni and Mo from a low-alloy steel. Fig. 3 GB enrichment maps (atoms/nm 2 ) of Ni and Mo from a low-alloy steel.

Nanosegregation, microtexture and the control of brittle failure David B. Williams and Masashi Watanabe, Lehigh University, MET DMR Broader Impact Atomic-resolution scanning transmission electron microscopy (STEM) imaging by remote control We have demonstrated the remote operation of a JEOL JEM-2200FS aberration-corrected STEM at Lehigh (the first such installation in the USA) in collaboration with JEOL USA (Peabody, MA), connected via fast internet from the Chicago Navy Pier Convention Center, where the Microscopy & Microanalysis 2006 annual meeting was held (note: both the PI and co-PI had invited presentations entitled “Atomic-Scale Characterization of Metals and Alloys Using Spherical-Aberration Corrected Scanning Transmission Electron Microscopy” and “Progress of Elemental/Compositional Mapping via X-rays and Energy-Loss Electrons in Analytical Electron Microscopes” at this meeting, respectively). During this demonstration, we showed the seamless microscope operation (Fig. 1) and performed atomic- resolution STEM imaging of SrTiO 3 (Fig. 2) despite the non-ideal conditions on the floor of the convention center and the separation of 700 miles. This successful remote microscope operation further enhances prospects for real-time, long-distance experiments involving such as international partnerships, dynamic teaching of microscopy during classes and live microscope demonstrations for undergraduate and/or middle high-school students are possible and broadens the availability of high-end, expensive instrumentation. Fig. 1 (top) An image showing the remote operation of Lehigh’s microscope from Chicago. Fig. 2 (right) An atomic-resolution STEM image from SrTiO 3 taken during the remote operation. The brighter and darker spots correspond Sr and Ti atom positions, respectively. 3.6 Å