Improvement of low cycle fatigue properties with addition of Ti in 321 stainless steels

The continuous low cycle fatigue behaviors of 321 stainless steels with various compositions of Ti and carbon have been evaluated at test temperatures of 873 and 973K under a controlled total strain range. After low cycle fatigue tests, the effects of Ti in the matrix are investigated through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is found that higher Ti added 321 stainless steel has a longer low cycle fatigue life than lower Ti added 321 stainless steels with decreasing total strain range at both 873 and 973K. It was observed that fatigued specimens show transgranular fracture mode regardless of test temperature and strain range. With increasing Ti additions, the value of the fatigue ductility exponent decreases, subsequently leading to the increase in the low cycle fatigue life. Microstructural analysis indicates that Ti plays a major role in inhibiting crack propagation and dislocation movement in the lower strain range.