A Microstructural Characterization of as-Cast and Rapidly Solidified Titanium-Silicon Alloys (Silicide, Melt-Spinning, Precipitation, Metastable, Oxygen)

Rapid Solidification (RS) studies have been carried out on a number of Titanium-Silicon alloys. Two techniques have been employed to produce rapidly solidified material, namely laser surface melting and melt-spinning. Prior to RS, a careful microstructural characterization of the as-cast material was undertaken. This also involved a study of an homogenized and heat treated base alloy (Ti-2 wt%Si) to determine the types of precipitation reactions present in conventionally processed material. In the base alloy the equilibrium silicide in the temperature range 773 K - 1023 K was found to be Ti(,5)Si(,3) which would precipitate out of solid solution in accordance with two different orientation relationships. A tetragonal phase of chemical composition Ti(,3)Si was observed in the as-cast hypoeutectic alloys; however, it proved to be metastable and dissolved upon heat treatment (773-1023 K), resulting in an equilibrium microstructure consisting of (alpha)-Ti and Ti(,5)Si(,3). The as-cast microstructures of an eutectic and an hypereutectic alloy were also examined. Upon arc-melting both of these alloys exhibited an eutectic microstructure of Ti(,5)Si(,3) rods within an (alpha)-Ti matrix.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Metallurgical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Chumbley, Leonard Scott

• Engineering, Metallurgy

Identifier

(UMI)AAI8623272

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/71831