Recrystallization in subsurface zone seen by positron annihilation

The paper presents studies of the defect distribution, detected by the positron annihilation method in the subsurface zone (SZ) of copper samples after dry sliding wear. It takes advantage of a new experimental technique based on scanning of the positron implantation profile. It allowed us to detect the defect profile in copper to the depth of 200 μm in a nondestructive way and study isochronal annealing behavior of this profile. We determined that annealing induces a recrystallization process which runs faster close to the surface than in deeper regions. After sliding, the complete recrystallization of the substructure takes place at temperature c.a. 600 °C. Some changes in the defect structure begin at temperature c.a. 300 °C. The comparison of the temperature depth profile calculated theoretically with experimental results indicates that the role of the temperature rise in the asperity regions during sliding is negligible in the SZ constitution in the case studied.