Effect of Cluster-Hardening on Strength and Formability of Aluminum Alloys

This thesis addresses the development and optimization of aluminum alloys, focusing on overcoming the critical trade-off between strength and ductility to meet the requirements of the automotive and aerospace industries. The research investigates both 6xxx series alloys and novel 5/7 crossover alloys. While 6xxx alloys are optimized for their balanced strength and ductility, 5/7 crossover alloys combine the advantages of 5xxx series alloys' excellent formability with the high strength of 7xxx series alloys. For further advancements in this area, this work investigates the behavior of clusters and precipitates during deformation, highlights the cluster-hardening potential in 6xxx alloys and explores the clustering mechanisms in 5/7 crossover alloys. Through comprehensive analysis, the research reveals the critical role of clusters and precipitates in strengthening aluminum alloys. The inclusion of Cu significantly influences cluster nucleation, stability and precipitation behavior, leading to enhanced hardenability and mechanical perfomance. The interplay between clustering and deformation is explored in depth, demonstrating how deformation-induced clustering refines the microstructure and enhances the strength-ductility balance. For 6xxx alloys, this work demonstrates the potential of cluster hardening to achieve strength levels comparable to the T6 state, while significantly increasing elongation. This superior combination makes these alloys highly suitable for structural components in automotive and aerospace applications. The exploration of 5/7 crossover alloys revealed that, in addition to the inherent combination of the high strength of 7xxx alloys and the excellent formability of 5xxx alloys, cluster hardening further enhances the balance of strength and elongation, achieving yield strengths of 400 MPa alongside improved ductility. These findings underscore the importance of understanding microstructural transformations during processing and deformation to design alloys capable of meeting the demands of complex manufacturing environments. By advancing knowledge of clustering behavior, precipitation mechanisms and deformation processes, this thesis provides a framework for designing high-performance aluminum alloys. These innovations address the mechanical challenges faced by the automotive and aerospace industries, offering solutions that bridge the gap between strength and ductility, enabling the production of lightweight, high-performance components for next-generations engineering applications.