Study of the cyclic softening of an under-aged gamma'-precipitated nickel-base superalloy (Waspaloy)

Abstract
This study deals with the cyclic behaviour at room temperature of a nickel-base superalloy, strengthened by shearable γ precipitates. A special attention is paid to the influence of the controlled plastic strain ε_a. Whatever ε_a, a softening of the stress amplitude follows the first cycles hardening stage. This phenomenon is discussed in terms of back and effective stress evolutions. The decreasing of the total stress amplitude is mainly carried by the kinematic stress lowering, except for the lowest plastic strain level (0.05%), where the isotropic stress decreasing predominates. With the help of dislocations features, the interna1 stress is analyzed as a consequence of simultaneous activation of several slip systems.