Identifier

etd-07092016-215445

Degree

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

Document Type

Dissertation

Abstract

Accurate high-temperature thermophysical property data for liquid metals and alloys are important for simulation of laser-based 3D printing processes. To understand and better control such additive manufacturing processes, knowledge of density, viscosity, and surface tension of liquid metals and alloys versus composition and temperature is needed. Likewise, thermochemical property data information regarding alloys, including chemical activities and free energies relative to composition and temperature, aid in the understanding and development of phase data important in the material design process. Vacuum electrostatic levitation (ESL) is an important technique through which both thermophysical and thermochemical property measurements can be accomplished without physical contact with the liquid. We performed ESL measurements on molten Ti-based alloys, including elemental Ti, Ti-xAl binaries (x = 0-10 percent weight), Ti-6Al-4V, and Ti-6Al-4V-10Mo, through a container-less oscillating drop technique at the NASA Marshall Space Flight Center. Ti-Al-V-Mo quaternary alloy was studied for laser-based 3D printing, and showed improved mechanical properties over traditional β Ti alloys. Results for elemental Ti, Ti-xAl, and Ti-6Al-4V are compared with previously published results, while those for Ti-6Al-4V-10Mo are reported here for the first time. Additional thermodynamic data are generated for binary Ti-Al, and compared to CALPHAD results while viscosity and density values of liquid titanium were calculated via molecular dynamics and compared to experimental values. The test and simulation procedure developed provides a framework for the development of new and higher-order alloys in the high temperature regime and in the liquid phase.

Date

2016

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Guo, Shengmin

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