Modeling of Microstructure Evolution in Metallic Multilayers with Immiscible Constituents

Abstract

Thermal stabilities of Cu/Nb, Cu/Ag, and Cu/Mo multilayers are studied by a recently developed model for microstructure evolution in multilayers with immiscible constituents, which actually is an extension to the classic grooving theory. The experimentally evidenced zig–zag microstructure is found to form through grooving when grains are staggered in a “stair-like” fashion. Furthermore, stability maps for these systems are developed in terms of the aspect ratio of grain dimensions and the ratio of the distance between two nearest triple junctions to the in-plane grain size. A comparison of stability among the three systems shows that the ratio of the grain boundary energy to the interphase boundary energy is more important than the ratio of the two grain boundary energies in controlling the stability. A simple criterion is also proposed for a quick estimation of the stability. Both maps from the model and from the simple criterion are in good agreement with the experiments for multilayers.