Monday, September 8, 2008, 10:00 am — Bldg. 735 - Conf Rm A
Aluminum alloys with Cu and Mg as the main alloying elements constitute a group of technologically important lightweight structural material due to their excellent strength properties. The key microstructural features responsible for the excellent strength properties are rod-like metastable particles, known as GPB and GPBII zones. In this presentation, the unresolved issues regarding the structure of the GPB and GPBII zones will be addressed with the use of STEM HAADF imaging and ab initio calculations. It will be shown that the structure of GPB zones is unique, representing an agglomeration of structural units with one-dimensional translational periodicity. The structure of these basic units was fully determined with the aid of ab-initio calculations. On the other hand, it will be shown that structure of GPBII is closely related to a conventional crystal with hexagonal symmetry, space group P62m, lattice parameters a=0.7nm and c=0.4nm.
In the second part of the talk, an application of high-resolution imaging to study interfaces will be presented. In particular, coherency of S-phase in Al-Cu-Mg alloys and twinning in Ni based superalloys will be addressed.
Hosted by: Yimei Zhu
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