Date of Award

5-2018

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Engineering Technology

Committee Chair

Xiaoming Wang

Committee Co-Chair

Sarah Leach

Committee Member 1

Qingyou Han

Abstract

My research question is the effects of scandium on the formation and distribution of in-situ TiB2 particles in an aluminum matrix. In-situ TiB2 particles have been proven to be effective grain refiners in an aluminum matrix. On the other hand, scandium is getting more and more attention due to the high strength and low density of Al-Sc alloys, which have been applied in many areas. My research is to investigate the effect of the addition of scandium on the in-situ TiB2 particles in an aluminum matrix through a series of metal-salt reactions followed by a detailed microstructure analysis. TiB2 particles were formed by an in-situ method in an aluminum matrix via chemical reactions between an aluminum melt and the mixture of K2TiF6 and KBF4 salts. The investigation of Sc addition on the formation of the TiB2 particles revealed different coarsening mechanisms depending on the participation of Sc at different stages during the formation of the TiB2 particles. The presence of Sc in the metal-salt reactions resulted in an overall layered boride phases along the α-Al grain boundaries, while the addition of Sc after the metal-salt reactions broke up the boride layers improving the dispersion of the TiB2 particles. Scandium promoted the nucleation and growth of the TiB2 particles, resulting in the coarsening of TiB2 particles. The participation of Sc in the formation of the TiB2 particles altered the coarsening of the TiB2 particles, resulting in different morphologies of the TiB2 particles. The effect of holding time will also be covered in this research by applying two different holding times during the metal-salt reaction.

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