Abstract: Microstructure observation and nano-indentation test were carried out on crack arresting specimens of 304 stainless steel with and without plastic zone near the crack tip. The results show that phase transformation and recrystallization are found to occur at the crack tip of 304 stainless steel with plastic zone after pulse current arrest, and the solidification zone, fine grain zone and deformation-induced martensite zone are formed under the co-action of the temperature field and the stress field. However, the solidification zone is only occurred in the specimen without the plastic zone. The nano-indentation test shows that the fatigue crack tip of 304 stainless steel has large residual stress, which decays rapidly with the increment of the distance from the crack tip. After pulse current crack arrest, the formation of deformation-induced martensite leads to the increase of both the volume expansion and the compressive stress around the arrest crack, which is beneficial to suppress the crack propagation.

Key words: 304 stainless steel, plastic zone, crack arrest, nanoindentation, deformation-induced martensite