Interface Adhesion: Effects of Plasticity and Segregation

Abstract—The adhesion at interfaces between dissimilar materials is strongly aected by both segregation and the extent of plasticity in the adjoining material, particularly when one of these is a metal (or thermo-plastic). It will be shown that these interfaces when clean, are generally strong and tough, such that failure occurs in one of the adjoining materials, rather than at the interface. However, segregrants and contami-nants often embrittle and weaken the interface, especially in combination with ambient moisture. The em-brittlement is obviated either by alloying with elements that ‘‘getter’ ’ the contaminants or by using an ‘‘adhesion layer’ ’ that has essentially the same eect: Cr and Ti are particularly eective gettering elements. Models that relate these eects to fundamental material parameters through non-dimensional indices are described. They comprise linkages between atomistic and continuum, enabled by implementation of a plas-ticity length scale, within the context of a crack growth simulation routine. Comparison with the exper-imental results is conducted, leading to suggestions for development of a predictive scheme. # 1999 Act