Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10672648 | Ultramicroscopy | 2005 | 9 Pages |
Abstract
Field ion microscope images have been used to measure the local evaporation field of a Al3Zr particle in 7050 Al alloy. Using the matrix Al evaporation field (19Â V/nm) as a reference, the evaporation field of Al3Zr has been estimated to be 36Â V/nm, similar to the theoretical value for the field evaporation of Al2+ or Zr3+ ions. A strong local magnification effect from the large difference in evaporation fields between the particle and matrix has been found to cause a severe distortion of the apparent particle morphology in a three-dimensional atom probe reconstruction when using parameters based on the Al matrix. Use of the measured evaporation field for Al3Zr has allowed accurate reconstruction of the morphology of the particle. A simple worst-case analysis predicts that trajectory overlaps increase with increasing cross-section of particle, and the calculated overlaps agree well with experimental estimates of â¼1.4-2.0Â nm for variations in the particle cross-section from 7 to 12Â nm. The chemical composition of Al3Zr in a 7050 Al alloy has been measured to be 64.8-67.7Â at% Al, 23.6-24.8Â at% Zr, 6.9-9.1Â at% Zn, 0.4-0.7Â at% Cu, 0.5-1.2Â at% Mg, with a (Al+Zn)/Zr ratio close to 3. Specimen analysis temperatures of either 25 or 80Â K show little effect on the measured chemical compositions of the particle.
Related Topics
Physical Sciences and Engineering
Materials Science
Nanotechnology
Authors
G. Sha, A. Cerezo,