Comparison of defect structures in Fe-Cu alloys by high-speed and low-speed deformation with the detection of Cu precipitates

In order to clarify the effect of deformation speed on the defect structure evolution in bcc metals, Fe-0.15wt%Cu and Fe-0.6wt%Cu alloys deformed at a high strain rate (4.3 x 105/s) and a low strain rate (67/s) were studied. The positron lifetime and coincidence doppler broadening (CDB) measurements were carried out to investigate the formation of vacancy-type defects and Cu precipitates before and after annealing. The size and the concentration of vacancy-type defects introduced by high-speed deformation were larger than those by low-speed deformation. The low-speed deformed specimen exhibited the faster recovery of vacancy-type defects. After annealing at 400 C, however, the recovery of vacancy-type defects and the formation of Cu precipitates became almost the same for both. This suggests that the recovery of vacancy-type defects introduced by high-speed deformation is easier than that by low-speed deformation because of the high density of sinks for vacancies. (orig.)