Void and helium bubble interactions with dislocations in an FCC stainless steel alloy: anomalous hardening and cavity cross-slip locking

The critical stress for cutting of a void and He bubble (generically referred to as a cavity) by edge and screw dislocations has been determined for FCC Fe_0.70Cr_0.20Ni_0.10—close to 300-series stainless steel—over a range of cavity spacings, diameters, pressures, and glide plane positions. The results exhibit anomalous trends with spacing, diameter, and pressure when compared with classical theories for obstacle hardening. These anomalies are attributed to elastic anisotropy and the wide extended dislocation core in low stacking fault energy metals, indicating that caution must be exercised when using perfect dislocations in isotropic solids to study void and bubble hardening. In many simulations with screw dislocations, cross-slip was observed at the void/bubble surface, leading to an additional contribution to strengthening. We refer to this phenomenon as cavity cross-slip locking, and argue that it may be an important contributor to void and bubble hardening.