Effect of Thermal Aging on Fatigue Crack Propagation Properties of Z3CN20-09M Stainless Steel
Microstructure evolution of ferrite phase in Z3CN20-09M,thermally aged at 400 ℃ for up to 20000 h,was investigated by TEM.The fatigue crack growth properties of thermally aged materials were studied and the influence of thermal aging time was discussed.Fracture surface analysis by SEM was performed to investigate the crack propagation micro mechanisms.TEM results show that Cr-enriched α' phases are precipitated in ferrite phase and increase with the increase of aging time.Fatigue crack growth rates are fitted by Paris law,and the fitted crack growth rates increase with the increase of aging time.The fitted parameter exponent n increases,while lnC decreases with the increase of thermal aging time,and exponent n is linearly fitted against lnC.The increase in crack growth rate is associated with brittle cleavage of the ferrite phase.