Cu-6wt.%Ni-3wt.%Al was solutionised at 1173 K, cold rolled to 50 % and aged at 773 K. Transmission electron microscopy indicates that ageing of this material results in an initial recovery of the deformed matrix followed by precipitation of β-NiAl and γ′ -Ni3Al and recrystallization. The γ′ precipitates show a uniform distribution everywhere except zones near grain boundaries and shear bands which serve as preferential nucleation sites for β-NiAl precipitates. The recrystallization fronts were found to cause dissolution of γ′ precipitates but during further ageing a secondary precipitation of γ′ phase in recrystallized areas was observed. The highest strength, i. e. σm = 590 MPa, σ0.2 = 520 MPa, was achieved after 6 · 103 s of ageing.
This work received the financial support from the Committee of Scientific Research (KBN) under the grant 7T08B 001 10, and from Foundation for Polish Science.
We are grateful to W. Baliga for experimental support and Dr. J. Morgiel for several helpful discussions.
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