Phase Transformations in Aluminum Alloys: Kinetics and Diagrams

This lecture discusses the kinetics of phase transformations in aluminum alloys, focusing on the TTT (Time-Temperature-Transformation) diagram. The instructor explains that near equilibrium temperature, the driving force for transformation is weak, resulting in slow transformations such as germination and growth. As temperature approaches absolute zero, thermally activated phenomena also slow down. The lecture introduces the TTT diagram, illustrating the start and finish lines of transformation during isothermal holding after rapid cooling. The instructor emphasizes the importance of avoiding the 'nose' of the TTT diagram during cooling to prevent unwanted transformations. The cooling process, particularly Newtonian cooling, is analyzed, highlighting the significance of heat transfer coefficients and the size of the material. The lecture concludes with a discussion on the precipitation of phases in aluminum-copper alloys, detailing the conditions under which different precipitates form and their stability. Overall, the lecture provides a comprehensive overview of the principles governing phase transformations in aluminum alloys.