Worcester Polytechnic Institute Electronic Theses and Dissertations Collection

Title page for ETD etd-042909-102711


Document Typedissertation
Author NameSymeonidis, Kimon
URNetd-042909-102711
TitleThe Controlled Diffusion Solidification Process: Fundamentals and Principles
DegreePhD
DepartmentMechanical 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/Defense2009-04-27
    Availability unrestricted

    Abstract

    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.  

    Files
  • symeonidis.pdf

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