Title page for ETD etd-12122008-142405


Type of Document Master's Thesis
Author Zeagler, Andrew
URN etd-12122008-142405
Title Structure and Processing Relations in Ni-W Amorphous Particle Strengthened Ni Matrix Composites
Degree Master of Science
Department Materials Science and Engineering
Advisory Committee
Advisor Name Title
Aning, Alexander O. Committee Chair
Reynolds, William T. Jr. Committee Member
Schultz, Jeffery P. Committee Member
Keywords
  • metal matrix composites
  • amorphous
  • particulate reinforcement
  • mechanical alloying
Date of Defense 2008-09-26
Availability unrestricted
Abstract
Reinforcing metals with compositionally similar amorphous particles has been found to create composites with good interfacial bonding. It is conceivable that significant additional strengthening in amorphous reinforced composites can be realized by creating high-aspect ratio reinforcements; attritor milling holds promise in this regard. In this work, mechanical alloying was used to produce equimolar Ni-W powder that became a composite of amorphous Ni-W with undissolved W crystallites. A mixture of nickel powder and ten volume percent amorphous Ni-W powder was blended by attritor milling for either one or three hours, compacted by combustion-driven compaction and sintered for up to fifty hours at 600ºC. Prolonged times at elevated temperatures led to crystallization of the amorphous reinforcement particles and dissolution of tungsten into the matrix. Vickers macrohardness tests on the sintered composites yielded lower-than-expected values. Microscopy after hardness testing revealed sliding of particles at their boundaries, indicating poor bonding between them. It is believed that the sintering process was compromised by contamination from organic vapor present in the tube furnace used. While attritor milling effected smaller reinforcement particles, the small increase in aspect ratio would likely have been insufficient to cause significant strengthening by shear load transfer.
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