This lecture covers the concepts of eutectics and peritectics, focusing on their significance in various alloys such as cast iron and aluminum-silicon. It begins by distinguishing between two types of eutectic growth: regular and irregular. The instructor presents a classical model for regular eutectic growth, highlighting the microstructural differences that arise from the interaction between phases alpha and beta. The lecture also discusses peritectic transformations, which involve solid-state diffusion and are typically slower and out of equilibrium. The instructor explains the mechanisms behind these transformations, including the role of solute diffusion and the impact of phase composition on microstructure. The lecture concludes with a summary of key points, emphasizing the importance of understanding these transformations for applications in materials science and engineering.