| In the previous investigations, it has been proposed that the cavities are nucleated at grain boundary due to the aggregation of the mechanically generated vacancies. For that model, the cavity nucleation factor was introduced to correlate the number of cavities and the plastic strain range from which athermal vacancies are generated. In this investigation, a discussion is proposed to clarify the characteristic property of the cavity nucleation factor for the dependence of the plastic strain range using the results of creep-fatigue test of solutionized AISI 304 and aged AISI 304 stainless steel at 873K. From the creep-fatigue test result, the effect of thermal aging is found to be beneficial relative to solution treatment, and it can be considered that the great amount of small carbides are precipitated at the grain boundaries during creep-faitgue tests in the solutionzed material, and they increase the cavity nucleation rate because they can be sites for the cavity nucleation. And, based on this result, it is found that the cavity nucleation factor is a function of the plastic strain range and the dependency is varying with the materials. Using this relation, the modified model for life prediction is suggested. |
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