Observation of Fatigue Crack Initiation Process in Austenitic Stainless steel by AFM

摘要

Slip-band formation and fatigue crack-initiation processes in a stainless steel were observed by means of atomic force microscopy (AFM). In the stainless steel, they were initiated in the slip bands near the grain boundaries. The slip distance could be evaluated from intrusion depth and slip band angle relative to the stress axis. The material, the distance increased linearly with the legalisms of the number of cycles. When the slip distance reached a critical value, a transgranular crack was initiated from the slip band, and the slope was changed with crack initiation. The slip distance at crack initiation was almost identical, and this critical value is about90 nm. In a -brass, this critical value was 380 run. Then this critical value is controlled by atomic binding energy or atomic spacing independent of microstructure of the material.