In-situ observation of the effect of the precipitate/matrix interface on the evolution of dislocation structures in CLAM steel during irradiation

• Structure evolution of ion and electron irradiated CLAM steels was in-situ studied.
• High-density fine MC precipitate may inhibit the fast growth of dislocation loops.
• Interface of precipitate/matrix acts as a sink trapping radiation-induced defects.
• The stability of precipitates under high-dose irradiation should be considered.

The key factor that affects the irradiation resistance of a material is its structure such as grain size and precipitates. Two types of China Low Activation Martensitic (CLAM) steels with a different number density of MC phase were pre-ion implanted and subsequently irradiated by electrons using ultra-high voltage electron microscope (HVEM). The effect of MC phase on the growth behavior of dislocation loops and the stability of pre-existing precipitates were investigated in situ and this may give some hints on the way to increase the ability against irradiation damage. The results show that a high number density of the fine MC phase improves the strength of the material and also helps to inhibit the fast growth of dislocation loops. The interface between the precipitate and the matrix acts as an effective sink to trap radiation induced point defects, which can possibly result in an improvement of irradiation resistance to some extent. However, the coarsening of precipitates because of radiation enhanced diffusion is another issue that needs to be seriously considered when developing a nuclear material.