Modelling of intergranular damage propagation

Abstract

The ultimate goal of grain boundary engineering with regard to the intergranular damage propagation is to find a relationship between the resistance to intergranular degradation of a polycrystal and the characteristics of the interface distribution. In this study, a new probabilistic approach for the intergranular damage propagation is proposed, which combines the analysis based on the percolation theory and the consideration of the crack path as a Markov chain. The study was performed by means of computer simulation. The following qualitative conclusions concerning the influence of the microstructural parameters of the grain boundary network on the likelihood of failure of a polycrystalline specimen have been drawn from this study: (1) The analysis of a microstructure's susceptibility to intergranular damage should be based on the determination of the maximum crack length possible in the microstructure rather than on the average crack length. (2) Under certain conditions, the behaviour of cracks can be analyzed within the framework of the percolation model. (3) The resistance to intergranular degradation depends both on the parameters of the grain boundary network and the conditions of crack nucleation. (4) The fraction of crack-resistant boundaries is not the only factor controlling the intergranular damage resistance. The spatial arrangement of grain boundaries, in particular the triple junction distribution, is important as well. (5) Crystallographic texture and the development of annealing twinning may improve resistance to intergranular damage in materials prone to annealing twinning.