Abstract
The grain boundary (GB) engineering for improvement of fatigue property in SUS316L austenitic stainless steel was investigated. The fatigue crack was predominantly nucleated at high energy random GBs. The low-Σ coincidence site lattice (CSL) GBs with the lower GB energy showed the higher resistance to fatigue crack nucleation. In-situ observations of fatigue crack propagation revealed that the local crack propagation rate strongly depends on the spatial distribution of GBs having different character and structure. The local propagation rate of fatigue crack in crossing CSL GBs became lower than when propagated across random GBs and in grain interior. The local propagation rate along CSL GBs was lower than that in grain interior, while the fatigue crack propagation was accelerated when the crack propagated along random GBs. The specimen with the higher fraction of CSL GBs showed the higher fatigue strength than the specimen with the lower fraction of CSL GBs.
