Plastic flow localization in h.c.p. Zr alloys on macro- and microscale levels

The regular features exhibited by plastic strain localization on macro- and microscale levels at the parabolic strain hardening stage are examined for commercial Zr alloys used in nuclear power industry. The plastic flow shows instability, which is manifested as oscillatory variation of space-time distributions of local strain patterns as revealed by speckle interferometry. It is shown that the periodic accumulation of deformation in the flow nuclei enhances the evolution of dislocation structure within the nuclei so that one of them becomes a prefracture zone in which necking would finally occur. The data obtained are discussed within the framework of a synergetic approach to plastic deformation evolution at the final flow stage.