Metal-matrix composites alumina effect

Monticelli, C. Zucchi, F. Brunoro, G. Trabanelli, G. (1997). Stress corrosion cracking behaviour of some aluminium-based metal matrix composites. Corrosion Science, Vol. 39, No. 10-11, pp. 1949-1963, ISSN 0010938X Muhamed Ashraf, P. Shibli, S. M. A. (2007). Reinforcing aluminium with cerium oxide A new and effective technique to prevent corrosion in marine environments. Electrochemistry Communications, Vol. 9, No. 3, pp. 443-448, ISSN 13882481 Niino, M. Maeda, S. (1990). Recent Development Status of Fxmctionally Gradient Materials. ISIJ International, Vol. 30, No. 9, pp. 699-703, ISSN 09151559 Nunes, P. C. R. Ramanathan, L. V. (1995). Corrosion behavior of alumina-aluminium and silicon carbide-aluminium metal-matiix composites. Corrosion, Vol. 51, No. 8, pp. 610-617, ISSN 00109312... 

The thermal treatment affected the crystal structure as well as the surface composition. We noticed that the samples calcined at higher temperature present much larger metal particles (in the range 80-100 nm) whereas the one calcined at 500 C mostly display particles that have an average diameter of a few nanometers. In the case of neat alumina, the crystal phase changes from y to 0. The addition of Ba or La in the alumina matrix diminishes this effect. The samples calcined at 500 °C and 1000 C present similar diffraction patterns. The only exceptions concern the peaks of PdO, which become sharper with higher calcination temperature. In these cases, the crystalline character of PdO particles is more pronounced. 

Of course, the micromechanical relations (bounds, approximations or fit models) presented in this chapter for the effective elastic properties are by no means restricted to the alumina-zirconia system but can be applied to many types of ceramies and eeramie composites. On the other hand they cannot be expected to be automatically applicable to matrix-inclusion type composites in cases where the matrix consists of nonlinearly elastic materials (polymers), viscoelastic materials (glasses or porcelain at high temperature) or elastoplastic materials (metals). In particular, they cannot be a priori expected to be justified for materials of biological origin, although their application to many of these materials, e g. bone, might be seductive and dictated by practical needs. With respect to the inherent anisotropy and the hierarchical microstructure of these materials [Ontanon et al. 2000], however, any mathematical modeling or description of their composition-structure-property relationships has to be performed with due caution. 

---