Phase transformations in a Cu–14.2Al–15.0Ni alloy

In the as-quenched condition, the microstructure of the Cu–14.2Al–15.0Ni alloy was D03 phase containing extremely fine L–J precipitates. Since both fine D03 domains with a/2〈1 0 0〉 anti-phase boundaries (APBs) and small B2 domains with a/4〈1 1 1〉 APBs could be observed, the D03 phase existing in the as-quenched alloy should be formed by an A2→B2→D03 continuous ordering transition during quenching. It is worthwhile to note that the a/4〈1 1 1〉 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 °C for longer times, the phase transformation sequence as the aging temperature increased was found to be (α+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.