The reversion of deformation-induced α′-martensite in tension-deformed 1.4301 (EN) stainless steel was investigated using positron annihilation spectroscopy. The Doppler broadening of the annihilation line and positron lifetime spectroscopy were applied to study defect structure and its annealing behavior in samples with a similar deformation level but varying in α′-martensite amount. The difference in α′-martensite was obtained by applying different deformation temperatures, i.e., liquid nitrogen temperature, room temperature, and 200 °C. The cumulative annealing of the tension-deformed samples and measurement of the positron annihilation characteristics show the gradual annealing of defects in the temperature range between 200 and 400 °C due to the recovery and recrystallization. However, in the temperature range between 450 and 650 °C, the generation of vacancy clusters which trap positrons is revealed. This temperature range coincides with the temperature range of α′-martensite reversion which is confirmed by microhardness and magnetization measurements. The detected large vacancy clusters consisting of 6–9 vacancies can occur at the interface between austenite and α′-martensite phases due to the volume contraction accompanying bcc/fcc change.

Surface mechanical attrition treatment (SMAT) was used to generate a gradient microstructure in commercial grade magnesium. Positron annihilation lifetime spectroscopy and variable energy positron beam measurements, as well as microhardness tests, electron backscatter diffraction, X-ray diffraction, and electrochemical corrosion tests, were used to investigate the created subsurface microstructure and its properties. It was found that SMAT causes an increase in dislocation density and grain refinement which results in increased hardness of the subsurface zone. The mean positron lifetime values indicate trapping of positrons in vacancies associated with dislocations and dislocation jogs. The increase of the SMAT duration and the vibration amplitude influences the depth profile of the mean positron lifetime, which reflects the defect concentration profile. Electrochemical measurements revealed that the structure induced by SMAT increases the susceptibility of magnesium to anodic oxidation, leading to the enhanced formation of hydroxide coverage at the surface and, as a consequence, to the decrease in corrosion current. No significant effect of the treatment on the residual stress was found.