INTERGRANULAR CAVITATION IN COPPER UNDER HIGH-TEMPERATURE CREEP, FATIGUE AND CREEP-FATIGUE CONDITIONS

Microstructural parameters of intergranular cavitation in copper specimens fractured at 773 K under creep, high-cycle fatigue and creep-fatigue conditions have been determined by quantitative metallographic analysis. The results show that the final creep fracture occurs when all the stressed volume of the specimen is critically damaged by intergranular cavitation. On the other hand, fatigue fracture occurs by single crack propagation and the fracture path is not primarily determined by the amount of cavitation. The role of cavitation thus increases with decrease in the cyclic stress component as demostrated by the fracture behaviour under creep-fatigue conditions. Finally, the application of the percolation model of cavitation has been discussed.