The effects of prestraining on high cycle fatigue strength of newly developed low alloy TRIP steels with different matrix structure and different retained austenite characteristics were investigated for the automotive applications. The prestraining in tension up to at most 10% increased fatigue limit of the TRIP steels, especially when the matrix was polygonal ferrite structure. It was considered that the polygonal ferrite matrix increased fatigue limit mainly due to TRIP of untransformed retained austenite and high compressive internal stress in the matrix, resulting from hard second phase on prestraining. On the other hand, a small increment in fatigue limit in the TRIP steel with bainitic ferrite lath matrix was supposed to be owing to the increased dislocation density on prestraining, with a small effect of TRIP of retained austenite and compressive internal stress in the matrix.
展开▼
