Document Type dissertation Author Name Symeonidis, Kimon URN etd-042909-102711 Title The Controlled Diffusion Solidification Process: Fundamentals and Principles Degree PhD Department Mechanical Engineering Advisors Diran Apelian, Advisor Makhlouf M. Makhlouf, Committee Member Richard D. Sisson Jr., Committee Member John L. Jorstad, Committee Member Nikolaos Gatsonis, Graduate Committee Rep Keywords Solidification techniques Wrought alloys Casting Date of Presentation/Defense 2009-04-27 Availability unrestricted
Aluminum based alloys can be broadly classified into two groups: casting alloys and wrought alloys. Wrought Al-based alloys exhibit superior physical and mechanical properties compared to the conventional shaped casting alloys. The wrought alloys cannot be cast into near net shapes, because they develop hot tears or hot cracks during the solidification process. For this reason these alloys are cast into ingots and are subsequently brought to final shape by mechanical processes like rolling, extrusion, drawing and forging. Invariably these processes significantly increase the cost of the final part up to 50%, and have restrained the application of the wrought alloys in applications where the cost is not a major factor. The CDS (Controlled Diffusion Solidification) is a novel process that bypasses the intermediate steps by casting the wrought alloy directly into final shape, free of hot tears, and eliminating additional deformation steps. The CDS process follows a different route from conventional casting methods. In CDS, two liquid metals of predetermined composition and temperature are mixed producing a globular microstructure instead of a dendritic one. The nondendritic microstructure minimizes the hot- tearing tendency and makes the wrought alloys more suitable to casting operations. The underlying principles and mechanisms of the CDS process have been established through both experimental work and the development of a mathematical model. The operating window of the process has been defined, and guidelines are proposed to enable application of the CDS process to various alloy systems. The reduction of the hot-tearing tendency in Al wrought alloys was experimentally verified.
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