MORPHOLOGY OF SILICON GRAIN-BOUNDARIES IN SR-MODIFIED AL-SI EUTECTIC ALLOYS BY HREM

Crystallographic changes in the SIGMA-3<110>/{111}, SIGMA-3<110>/{112} and SIGMA-9<110>/{112} boundaries induced by the presence of strontium in the silicon phase of Sr-modified Al-Si alloys have been studied by high-resolution electron microscopy. The SIGMA-3 boundaries possessing {111} and {112} planes in the pure silicon phase often exhibit asymmetric morphologies in the Sr-modified phase. Interaction of various SIGMA-3<110>/{111} boundaries results in both SIGMA-3<110>/{112} and SIGMA-9<110>/{112} boundaries. The resulting SIGMA-9 boundaries also show asymmetrical inclination.