Faculty Advisor

Diran Apelian

Faculty Advisor

Makhlouf M. Makhlouf

Faculty Advisor

Richard D. Sisson Jr.

Faculty Advisor

John L. Jorstad

Faculty Advisor

Nikolaos Gatsonis

Identifier

etd-042909-102711

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.  

Publisher

Worcester Polytechnic Institute

Degree Name

PhD

Department

Mechanical Engineering

Project Type

Dissertation

Date Accepted

2009-04-29

Accessibility

Unrestricted

Subjects

Solidification techniques, Wrought alloys, Casting

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