EFFECT OF ENVIRONMENTS ON FATIGUE BEHAVIOUR OF A DUAL-PHASE STEEL
环境对双相钢疲劳性能的影响

Corrosion fatigue behaviour of an as-rolled dual-phase steel has been investigated in tap water or 3.5%NaCl agueous solution under full immersion and intermittent wetting. It was found that in comparison with the data in air, expo- sure to either tap water or salt water results in a substantial reduction in fatigue life and intermittent wetting later shows the most harmful effects. However, under the same aggressive condition, the corrosion environments become more and more harmful while the stress level decreases. A combined observation of fracture surface with the flat free surface in SEM shows that corrosion fatigue cracks initiate often at corrosion pits resulted from the anodic dissolution. In addition, the inter- action between hydrogen and crack tip is considered another important factor which controls the crack initiation and propagation in corrosion fatigue. The mar- tensite exhibits a higher resistance to corrosion fatigue than the ferrite matrix.