Faculty Advisor or Committee Member

Makhlouf, M. Makhlouf, Advisor

Faculty Advisor or Committee Member

Diran Apelian, Committee Member

Faculty Advisor or Committee Member

Harold Brody, Committee Member

Faculty Advisor or Committee Member

Danielle Lynn Cote, Committee Member

Identifier

etd-050415-125629

Abstract

A castable alloy, i.e., one that flows easily to fill the entire mold cavity and also has resistance to hot tearing during solidification, must invariably contain a sufficient amount of a eutectic structure. For this reason, most traditional aluminum casting alloys contain silicon because the aluminum-silicon eutectic imparts to the alloy excellent casting characteristics. However, the solidus temperature in the Al-Si system does not exceed 577°C, and the major alloying elements (i.e., zinc, magnesium, and copper) used with silicon in these alloys further lower the solidus temperature. Also, these elements have high diffusivity in aluminum and so, while they enhance the room temperature strength of the alloy, they are not useful at elevated temperatures. Considering nickel-base super alloys, whose mechanical properties are retained up to temperatures that approach 75% of their melting point, it is conceivable that castable aluminum alloys can be developed on the same basis so that they are useful at temperatures approaching 350C. A castable aluminum alloy intended for high temperature applications must contain a eutectic structure that is stable at temperatures higher than 600°C, and must contain second phase precipitate particles that are thermodynamically stable at the service temperature. Transition metal trialuminides with the general chemical formula AlxTMy in which TM is a transition metal, are excellent candidates for both the eutectic structure and the precipitate particles. In this research, the use of transition metals in the constitution of aluminum casting alloys is investigated with emphasis on the morphology, crystallography, and mechanisms of formation of the various phases.

Publisher

Worcester Polytechnic Institute

Degree Name

PhD

Department

Materials Science & Engineering

Project Type

Dissertation

Date Accepted

2015-05-04

Accessibility

Unrestricted

Subjects

eutectic, Al-Mn, Al-Ni-Mn, Al-Mn-W, Al-Ni, Precipitation hardening. Al-Zr-V

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