Tensile and High‐Cycle Fatigue Properties of Steel Sheet with Trace Silicon

The tensile properties, high‐cycle fatigue properties, fracture surface morphologies, corresponding damage mechanisms, and dislocation patterns of two steels with trace silicon, 550TG and SD320, are investigated. It is found that the SD320 has a higher tensile strength than 550TG, but lower plasticity. In general, some deep cracks appear along the direction of rolling in all the tensile specimens and the fatigue limit of SD320 is higher. In particular, the 550TG shows a continuously decreasing S–N characteristic without fatigue limit at the higher cycle region, which can be explained by their differences of dislocation morphologies. Furthermore, the tensile and fatigue damage mechanisms are deeply analyzed and discussed.