CYCLIC DEFORMATION OF THE ALLOY CU-35-PERCENT-NI-3.5-PERCENT-CR IN THE HOMOGENIZED CONDITION

The cyclic deformation behaviour of the planar slip mode alloy Cu-35%N i-3.5%Cr in the homogenized condition has been investigated at constan t stress amplitudes. During cycling at stress amplitudes higher than t he cyclic yield strength, an initial cyclic hardening followed by a cy clic softening was observed. TEM studies revealed that cyclic hardenin g is due to an increase of dislocation density and cyclic softening is mainly introduced by energetically favourable rearrangements of dislo cations. The smallest plastic strain amplitude during cycling correspo nds to a saturation dislocation density, which increases with increasi ng stress amplitude. The lifetime of this alloy can be correlated not only with the stress amplitude, but also with the smallest plastic or total strain amplitude.