Characterization and modeling in light alloys and nano-bainitic steels

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Ever-increasing and stringent demands on advanced materials and processing technology in the automotive, aerospace, rail and defense industries pose enormous scientific and technological challenges. The newer advanced high strength steel alloys with vastly improved microstructures such as nano-bainitic steels have the potential to extend the use of steel to even more demanding applications in transportation, energy and defense sectors. Welding is the primary joining process in many of these applications and recent efforts have been directed in applying non-fusion welding techniques such as ultrasonic welding to the newer lightweight structural materials such as magnesium alloys in automotive and aerospace applications. The overall goal and long-term objective of this research program is to continue to make significant advances in the area of structure-property-transformation relationships with particular emphasis on the innovative solid-state welding processes and new promising nano-bainitic steels. Specifically, in this proposal the following will be studied: (i) process optimization of ultrasonic spot welding of dissimilar materials with special attention to the underlying mechanisms involving interface layer bonding, structure characteristics and properties, and (ii) development of new compositions and cost-effective heat treatment procedures for the nano-bainitic steels with superior combinations of strength with fracture resistance. Both experimental and modeling approaches will be adopted to make advances in these areas to further scientific understanding and to meet the demands of industry both through advanced research and through the training of HQP who are in high demand in industry and academia.