Date of Graduation

2003

Document Type

Thesis

Degree Type

MS

Committee Chair

Bruce S. Kang

Committee Chair

Bruce S. Kang

Abstract

A number of silicide-based intermetallics are currently being developed for high temperature applications (>1000°C) in advanced fossil energy combustion systems. These alloys consist typically of Mo3Si, Mo5SiB2, and a molybdenum solid solution phase. The Mo5SiB2 phase is required for oxidation resistance. The ductile molybdenum solid solution phase provides toughening. However, a fundamental limitation to their practical utilization is the requirement to maintain the desired high-temperature mechanical properties while also achieving the necessary high-temperature oxidation/hot corrosion resistance. The key challenge of the alloy development is to find the right combination of good oxidation and creep resistance, together with the necessary fracture toughness and ductility. The objective of this research is to study the thermomechanical properties of spinel dispersed molybdenum alloys. Tensile tests were carried out on dog-bone specimens at room temperature and at 650°C. To study the loading rate effects, two different loading rates were applied; slow loading rate (0.00254mm/min) and fast loading rate (0.254mm/min). Thermal cycling effects were also studied for alloys with dispersing spinel particles. Tensile tests for specimens subjected to either 10 or 20 thermal cycles were also conducted. For each tensile test, a follow-up detailed fractography and microstructural analysis were carried out. The test results were correlated to the size, density, distribution of the spinel particles and processing time.

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