Tensile and fatigue properties of ultrafine-grained low-carbon steel processed by equal channel angular pressing

High-strength ultrafine-grained low-carbon steel was processed by equal channel angular pressing (ECAP) for different passes and then heat-treated to achieve the tensile strength in the range of 1400-1500 MPa. Then its microstructure and mechanical properties, especially fatigue properties were systemically investigated. It is found that the simultaneous enhancement of tensile strength and elongation can be obtained by only one ECAP pass; the optimum fatigue strength of 460 MPa can be gained by two ECAP passes; while further increasing the number of ECAP passes made the fatigue properties worse. Therefore, combing with the effects of heat treatment and fatigue damage mechanism, it is suggested that few number of ECAP passes is enough to achieve the optimum fatigue properties for low carbon steel, which makes it easy, economical and efficient for the engineering application of ECAP.