A TEM STUDY OF A COPPER RICH PHASE GROWN ON AN AL3ZR DISPERSOID IN A SPRAY FORMED AL SIC COMPOSITE/

A copper rich aluminium zirconium phase encountered in a spray formed Al/SiC composite has been investigated. It was found to grow epitaxial ly on the (001) faces of the Al3Zr dispersoids. The measured concentra tions by EDS, down to an accuracy of 1% did not correspond to a known compound, the new phase has a composition of Al7Cu3Zr2. By careful dif fraction and image simulation, and comparison with experimental result s, we obtain a spatial group of P4/mmm and two very closely related at omic distributions inside the unit cell. The structure is close to tha t of Al3Zr with the same a parameter, however the a parameter is 1.157 nm.