Hydrogen-enhanced dislocation emission, motion and nucleation of hydrogen-induced cracking for steel

Abstract

The change in dislocation configuration ahead of a loaded crack tip before and after charging with hydrogen wasin situ investigated in TEM using a special constant deflection loading device. The results showed that hydrogen could facilitate dislocation emission, multiplication and motion. The change in displacement field ahead of a loaded notch tip for a bulk specimen before and after charging with hydrogen wasin situ measured by the laser moire interferometer technique. The results showed that hydrogen could enlarge the plastic zone and increase the plastic strain. Thein situ observation in TEM showed that when hydrogen-enhanced dislocation emission and motion reached a critical condition, a nanocrack of hydrogen-induced cracking (HIC) would nucleate in the dislocation-free zone (DFZ) or at the main crack tip. The reasons for hydrogen-enhanced dislocation emission, multiplication and motion, and the mechanisms of nucleation of HIC have been discussed.