The main objective of the present work is to explore the morphological changes in the eutectic silicon particles associated with the increase in the solution treatment time up to 400 h by quantifying the characteristics of the eutectic silicon particles at different durations of solution heat treatment. Thermal modification of silicon particles proved to be more effective in the Sr-modified alloys rather than their Sr-free counterparts. The evolution of silicon particles during extended solution treatments followed the same trends and sequences for non-modified and Sr-modified 354-type and 356 alloys, at different evolution rates. The coarsening of eutectic Si particles occurred through particle coalescence and Ostwald ripening mechanisms. While both mechanisms were active at the same time, however, they operated independently and additively. The pinholes observed in the silicon particles derive from the impression or imprint left behind from the diffusion of small particles into larger particles.