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URN etd-0828106-114016 Statistics This thesis had been viewed 2355 times. Download 558 times. Author Shuo-Jhang Hung Author's Email Address No Public. Department Materials Engineering Year 2005 Semester 2 Degree Master Type of Document Master's Thesis Language English Page Count 103 Title Preparation of In-situ Strengthening TiB2 in Conducting Cu-based Composites by Mechanical Alloying Keyword TiB2 Mechanical alloying Conducting Copper base Copper base Conducting Mechanical alloying TiB2 Abstract Pure copper has excellent electrical conduction property and uses extensively as a conductive material. However, the strength and wear property of the pure copper are so low that its use on the contact or electrode material is limited. In this study pure elemental powders of Cu, Ti, and B were used to fabricate high strength and high electric conductive Cu-based composites with TiB2 as strengthening particles by the mechanical alloying technique. The milled powders were sintered in a vacuum hot-pressing furnace in a reducing atmosphere. The experimental result shows that during the milling of the initial powders up to 30 hrs, Ti and B elements continuously dissolve into the Cu lattice. No new phases were detected in this period. TiB2 phase was only formed by the subsequent annealing. The quantity of TiB2 created depends mainly on the annealing temperature and has little dependence on the milling time. From the microstructural observation, increasing the hot-pressing time can effectively eliminate the pores present in the bulk materials. The results from EPMA analysis showed that the distribution of Ti and B elements on the Cu matrix was overlapped. Quantitative analysis showed that the relative content of these two elements was close to 2 to 1, which indicated that these two elements were combined to form TiB2 during the annealing process. The microstructure of the bulk sample has primarily two regions with different contrast. The white region is rich in Cu and the gray region contains, besides Cu, larger amount Ti and B atoms. Electron migration passes readily through the white Cu-rich region. Therefore, materials with greater white region will show greater conductivity and smaller resistivity. From the hardness values of the bulk samples, it is inferred that the hardness of the bulk sample is determined by the relative size of the white region and the gray region which contains TiB2 particles, the distribution of TiB2 in the gray region. Advisor Committee Hsin-ming Wu - advisor
Chia-gung Hu - co-chair
Pee-yew Lee - co-chair
Files Date of Defense 2006-07-24 Date of Submission 2006-08-28