Influence of thermal aging on the deuterium permeation and retention behavior in the CLAM Steel

• Thermal aging of CLAM steel at 923 K for 8000 h affects deuterium permeation and retention behavior. • Deuterium retention in CLAM steel decreases, while permeability increases after thermal aging. • The changes in deuterium behavior are attributed to dislocation and sub-grain evolution in CLAM steel. As one of the candidate structural materials for the fusion reactor, the properties of China Low Activation Martensitic (CLAM) steel gradually degrade during service at high temperature. While the effects of thermal aging on the mechanical properties of CLAM steel have been widely studied, the behavior of deuterium permeation and retention in CLAM steel after thermal aging is not yet well understood. In this study, the CLAM steel was exposed to 923 K for 8000 h. Subsequently, thermal desorption spectroscopy (TDS) and gas-driven permeation (GDP) experiments were performed to investigate the evolution of deuterium permeation and retention in CLAM steel following thermal aging. The results showed that the deuterium retention in CLAM steel decreased after thermal aging for 8000 h, while the deuterium permeability of aged CLAM steel increased. The further microstructural characterization reveals that dislocations, which serve as deuterium trapping sites, evolve into sub-grain boundaries during the thermal aging process. The grain boundaries, acting as rapid diffusion paths for deuterium atoms, lead to an increase in permeation and a decrease in retention.