It was reported in the previous paper that the crack morphology of the stress corrosion cracking of 18-8 austenitic stainless steel in a boiling 42% magnesium chloride solution changed with applied stress level.
In this paper it was intended to attest that this transformation depends upon the stress intensity factor at the crack tip, and to inspect whether the crack propagation proceeds along a particular crystallographic orientation or not.
The ratio of intergranular cracking to transgranular one was measured on the single notched specimens fractured under various initial loads such as 300, 400 and 600kg.
The relation between the crack morphology and the stress intensity factor at the crack tip was also obtained, and the dependency of the crack propagation upon the crystallographic orientation was inspected by forming etch pits on the cracked surface of the specimen fractured under the initial load of 300kg.
The following conclusions were deduced from these experiments: The crack morphology transformed remarkably from transgranular cracking to intergranular cracking with increasing applied stress or the stress at the crack tip under the same applied stress, and the degree of transformation was highly connected with the stress intensity factor at the crack tip.
The transgranular cracking in the region of low stress was likely to be formed by crack growth along <110> direction on {110} planes, and the facets formed on this crack surface were likely associated with this dependency of crack propagation upon crystallographic orientation. These results indicate that this crack morphology was formed by the anodic dissolution of sessile dislocations and tearing by stress.
