Selective phase formation in substoichiometric Al-Cr-based oxides.

The transition from (inter)metallic to substoichiometric regime and therewith associated microstructural modifications within arc evaporated Al-Cr-based oxide coatings was investigated. The dense columnar intermetallic structure is subject to grain refinement when increasing the O 2 flow rate during the deposition. Cr-rich, O-depleted crystalline domains (initially short columnar, then equiaxed globular) and an amorphous Al- and O-enriched boundary phase develops—with increasing volume fraction for higher O 2 flow rates. Such nanocomposites, originating from preferred oxide phase formation of Aluminium, can effectively be adjusted by the amount of oxygen and the nominal cathode composition used during synthesis. [ABSTRACT FROM AUTHOR]