Positron annihilation study on interaction between hydrogen and defects in AISI 304 stainless steel

Interaction between hydrogen and defects in AISI 304 stainless steel was investigated by positron annihilation lifetime spectra (PALS) and coincidence Doppler broadening (CDB) measurements. PALS results show that long lifetime component τ2 is about 260–270 ps, and does not change with current density, which is ascribed to the formation of three-dimensional vacancy cluster of 5–7 vacancies. Furthermore, the CDB ratio curves show that an obvious peak appears in the high-momentum region after hydrogen charging, and the peak site does not vary with current density. The mechanism of interaction between hydrogen with defects is discussed.