Phase transition in a Cu–14.1Al–9.0Ni alloy

The phase transition of the Cu–14.1 wt.% Al–9.0 wt.% Ni alloy has been examined by transmission electron microscopy and energy-dispersive X-ray analysis. In the as-quenched condition, the microstructure of the alloy was D03 phase that contained extremely fine L-J precipitates. During the early stage of isothermal aging at 500 °C, a high density of the extremely fine B2 particles was observed within the extremely thin lamellar γ1′ martensite, which was formed by a D03→γ1′ martensitic transformation during quenching. With increasing aging time at 500 °C, the isothermal phase transition sequence was found to be D03→D03+B2→D03+B2+α→B2+α+γ2. This transition significantly differs from that observed by other researchers. Besides, both Kurdjumov–Sachs (K–S) and Nishiyama–Wassermann (N–W) orientation relationships between the B2 particle and the α phase could be detected in the aged alloy.