High-resolution electron microscopy was employed to characterize the interface structure of a cast Al-Mg-Si-Bi-Pb aluminium(6262)-based composite reinforced by Î± alumina particles with a trace of Î² alumina in order to investigate the behaviour of alloying elements in cast composites. Except for a few primary Mg2Si particles, few reaction products were detected at the interface of Al/Î±-Al2O3 due to the unfavourable reaction kinetics during the squeeze-casting process. The Mg2Si particle has an orientation relationship with Î±-Al2O3 of Mg2Si//-Al2O3 (111)Mg2Si//(0006)-Al2O3. A significant amount of MgAl2O4 was found on the surface of the Î²-Al2O3 particles, which is in contrast to the small degree of reaction found on Î±-Al2O3 particles. MgAl2O4 and Î²-Al2O3 particles have the following orientation relationship: MgAl2O4//-Al2O3 (111) MgAl2O4//(0006)-Al2O3. The similar crystal structure of Î²-Al2O3 to MgAl2O4 favours MgAl2O4 nucleation and growth on the surface of Î²-Al2O3. Interfacial energy minimization dominates the atomic structure of the interface with the result that close packed planes and directions in the Al2O3 reinforcement and reaction products are parallel to the interfaces. Bi and Pb were found in the form of metallic nanometre particles between Al2O3 particles, or between the MgAl2O4 and Al2O3 particles, or in the open channels of Î²-Al2O3 filled by the Al matrix.
|Translated title of the contribution||High-resolution electron microscope observation of interface microstructure of a cast Al-Mg-Si-Bi-Pb(6262)/Al203p composite|
|Pages (from-to)||144 - 152|
|Number of pages||9|
|Journal||Journal of Microscopy|
|Publication status||Published - Feb 2001|