Interface adhesion: Effects of plasticity and segregation

The adhesion at interfaces between dissimilar materials is strongly affecte d by both segregation and the extent of plasticity in the adjoining materia l, particularly when one of these is a metal (or thermoplastic). It will be shown that these interfaces when clean, are generally strong and tough, su ch that failure occurs in one of the adjoining materials, rather than at th e interface. However, segregrants and contaminants often embrittle and weak en the interface, especially in combination with ambient moisture. The embr ittlement is obviated either by alloying with elements that "getter" the co ntaminants or by using an "adhesion layer" that has essentially the same ef fect: Cr and Ti are particularly effective gettering elements. Models that relate these effects to fundamental material parameters through non-dimensi onal indices are described. They comprise linkages between atomistic and co ntinuum, enabled by implementation of a plasticity length scale, within the context of a crack growth simulation routine. Comparison with the experime ntal results is conducted, leading to suggestions for development of a pred ictive scheme. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Scienc e Ltd. All rights reserved.