Abstract
Atom probe tomography was utilized to measure directly the chemical compositions of Al3(Zr1-xTix) precipitates with a metastable Ll2 structure formed in Al-0. 1Zr-0.1Ti (at.%) alloys upon aging at 375°C or 425°C. The alloys exhibit an inhomogeneous distribution of Al3(Zr1-xTix) precipitates, as a result of a nonuniform dendritic distribution of solute atoms after casting. At these aging temperatures, the Zr:Ti atomic ratio in the precipitates is about 10 and 5, respectively, indicating that Ti remains mainly in solid solution rather than partitioning to the Al3(Zr1-xTix) precipitates. This is interpreted as being due to the very small diffusivity of Ti in α-Al, consistent with prior studies on Al-Sc-Ti and Al-Sc-Zr alloys, where the slower diffusing Zr and Ti atoms make up a small fraction of the Al3(Sc1-x/Tix/Zrx) precipitates. Unlike those alloys, however, the present Al-Zr-Ti alloys exhibit no interfacial segregation of Ti at the matrix/precipitate heterophase interface, a result that may be affected by a significant disparity in the evaporation fields of the α-Al matrix and Al3(Zr1-xTix) precipitates and/or a lack of local thermodynamic equilibrium at the interface.
Original language | English (US) |
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Pages (from-to) | 503-516 |
Number of pages | 14 |
Journal | Microscopy and Microanalysis |
Volume | 13 |
Issue number | 6 |
DOIs | |
State | Published - Dec 2007 |
Keywords
- Al-Zr-Ti
- AlZr precipitates
- Atom probe tomography
- Local magnification
ASJC Scopus subject areas
- Instrumentation