Phase transformations in a Cu-142Al-15.0Ni alloy

Abstract

In the as-quenched condition, the microstructure of the Cu-14.2Al-15.0Ni alloy was D0(3) phase containing extremely fine L-J precipitates. Since both fine D0(3) domains with a/2(100) anti-phase boundaries (APBs) and small B2 domains with a/4(111) APBs could be observed, the D0(3) phase existing in the as-quenched alloy should be formed by an A2 --> B2 --> D0(3) continuous ordering transition during quenching. It is worthwhile to note that the a/4(111) APBs have never been observed by other workers in the Cu-Al-Ni ternary alloys before. When the as-quenched alloy was aged at temperatures ranging from 400 to 1000 degreesC for longer times, the phase transformation sequence as the aging temperature increased was found to be (alpha + B2 precipitate) --> (B2 + B2 precipitate) --> B2 --> A2. This transformation has also never been observed by other workers in the Cu-Al-Ni ternary alloys before. (C) 2002 Elsevier Science B.V. All rights reserved.