(University of Alabama Libraries, 2010) Morris, Robert Allen; Thompson, Gregory B.; University of Alabama Tuscaloosa
Transition metal carbides have a large assortment of applications because of their high hardness, chemical resistance, and high melting temperatures. Tantalum carbide (TaC) and its sub-stoichiometric Ta2C and Ta4C3 phases have emerged as candidate materials for ultra-high temperature structural applications. A consequence of the high melting temperature is the limiting methods to fabricate near-net shape, near full density tantalum carbides. In general, hot-isostatic pressing (HIP) and/or arc melting/vacuum plasma spraying (VPS) of powders are the viable means of manufacturing. In HIP'ing, the phase formation is through solid-state reactions whereas arc melting/VPS involves rapid solidification. Additionally, the precipitation of multiple phases generates various orientation relationships that influence the grain morphology. Depending on carbon content, the grains were equiaxed, equiaxed with a cross-hatch pattern of thin laths of secondary phases, to acicular grains. The microstructures were quantified through a series of different 2D and 3D analytical techniques. To understand how these microstructures developed, a series of XTa:(1-X)C (0.5