TEM STUDY OF THE FIBER CROSS-SECTION ATTACK IN DELTA-AL2O3 MG8LI METAL-MATRIX COMPOSITES/

During manufacturing of delta-Al2O3/Mg8Li composites by melt infiltrat ion reactive diffusion of Mg and Li into the fibre bulk takes place. N o remarkable reaction zone was found at the fibre periphery, although, a Mg enrichment zone (approx. 100 nm thick) was detected there by EDX and EELS. In addition, MgO, Li2O and Mg2Si minority phases were ident ified by SAED within the fibre cross-section. The crystalline structur e of the delta-Al2O3 fibres in the Mg8Li matrix remained of the alumin a spinel type at all the time, however, a set of crystallographically coherent products assigned as gamma(Li) was detected by XRD and SAED w ithin the fibre cross-section. As believed, the gamma(Li) results from topotactic Li+ incorporation into the delta-Al2O3 lattice so that no significant changes in terms of size and morphology of the alumina cry stallites are observed.