PRECIPITATION AND RECRYSTALLIZATION PROCESSES DURING AGING OF PLASTICALLY DEFORMED CU-6WT.PERCENT NI-3WT.PERCENT AL

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 matri x followed by precipitation of beta-NiAl and gamma'-Ni3Al and recrysta llization. The gamma' precipitates show a uniform distribution everywh ere except zones near grain boundaries and shear bands which serve as preferential nucleation sites for beta-NiAl precipitates. The recrysta llization fronts were found to cause dissolution of gamma' precipitate s but during further ageing a secondary precipitation of gamma' phase in recrystallized areas was observed. The highest strength, i. e. sigm a(m) = 590 MPa, sigma(0.2) = 520 MPa, was achieved after 6 . 10(3) a o f ageing.