High strength material performance at elevated temperatures is a critical concern in the design of power generating systems. The micromechanics of material failure near the tip of a macroscopic crack will be analyzed. At elevated temperatures, cracks usually propagate along grain boundaries that have been weakened by the nucleation and subsequent growth of cavities. The objective of this research is to analyze in detail the nucleation and growth of cavities near pre-existing cracks and to determine the effects of size and spacing of second-phase particles which nucleate cavities (e.g., carbides or sulphides) on the conditions for crack propagation. The solution of such problems will improve our basic understanding of the micromechanisms responsible for material failure at elevated temperatures and will identify macroscopic fracture parameters.
