Thin-Film Model Studies of Interfacial Reactions in Intermetallic Matrix Composites.

摘要

This study strongly suggests that the likelihood of nanoscale interfacial reactions in stable systems is greater than anticipated. This finding appears to contradict existing evidence of BULK non-reactivity in most of these systems (except TiAl/TiC). There may be a number of reasons for this apparent contradiction between bulk and thin-film results. For example, the resolution of the techniques used in bulk studies may be too poor to detect nanometer-scale reaction products; the reactions may be self limiting, with the product phase becoming an efficient diffusion barrier preventing further layer growth. Thin-films may differ chemically from bulk, affecting the reactivity, although comparisons of TiAl (film) reactions with thin Al2O3 films and with sapphire show that if anything, the sapphire is more reactive. We suggest however that the existence of nanoscale reactions at supposedly stable interfaces should be considered the norm, rather than the exception, particularly at the high temperatures of IMC preparation or use.