Creep Behavior of a Zirconium Diboride-Silicon Carbide Composite and Preliminary ZrB2-WC Quasi-Binary Alloy Development for Long Duty Cycle Aerosurfaces and Structural Propulsion Applications
| dc.contributor.advisor | White, Kenneth W. | |
| dc.contributor.committeeMember | Becher, Paul F. | |
| dc.contributor.committeeMember | Sharma, Pradeep | |
| dc.contributor.committeeMember | Sun, Li | |
| dc.contributor.committeeMember | Wheeler, Lewis T. | |
| dc.contributor.committeeMember | Willam, Kaspar J. | |
| dc.contributor.committeeMember | Litvinov, Dmitri | |
| dc.contributor.committeeMember | Khator, Suresh K. | |
| dc.creator | Bird, Marc W. 1984- | |
| dc.date.accessioned | 2016-02-15T02:43:18Z | |
| dc.date.available | 2016-02-15T02:43:18Z | |
| dc.date.created | December 2013 | |
| dc.date.issued | 2013-12 | |
| dc.date.updated | 2016-02-15T02:43:18Z | |
| dc.description.abstract | The mechanical behavior of select ultra-high temperature ceramics were studied for extreme environment aerospace applications. Hot-pressed ZrB2-20 vol% SiC composites and ZrB2-WC quasi-binary alloys were developed for assessing room temperature mechanical properties and creep behavior. A thermochemical model describing alloy phase stability and reaction equilibria, for promoting WC dissolution, is presented. Room temperature structure-property relationships were developed correlating fracture strength and KIC with microstructure constituent size. Flexural creep studies of ZrB2-20 vol% SiC were conducted over the range of 1400°C to 1820°C assessing the macroscopic creep behavior using power-law stress and temperature dependent constants. Inert environment creep experiments were conducted for probing the local grain deformation mechanism in anticipation of bridging the deformation length scales. A two decade increase in creep rate, between 1500 and 1600°C, suggests a clear transition between the low temperature (1400-1500°C) diffusion creep and high temperature (>1600°C) grain boundary sliding creep having stress exponents of unity and 1.7<n<2.2, respectively. A novel indentation deformation mapping experiment clearly defined the local ZrB2 grain boundary sliding event with its components of 80% grain translations and rotations and 20% grain deformation. EBSD and texture theory confirmed the direct observation of ZrB2 grains deforming by dislocation flow, confined to near-grain boundary (mantle) zones, accommodating the grain rotation and translation events. A transition from the grain core to mantle deformation deviated from single crystal behavior as a result of extra geometrically necessary dislocations accommodating the deformation gradient. Microstructure observations shows evidence of <5% and <20% SiC grain deformation, contributing to the macroscopic creep strain, for tension and compression bending fibers, respectively. Cavitation accounts for less than 5% contribution to the accumulated creep strain. Preliminary ZrB2-WC quasi binary alloy creep experiments reveal a decade decrease in the steady state creep rate with a 1.1 mol% increasing WC composition. Improved creep behavior is discussed in the context of solute interactions with accommodation dislocations from grain boundary sliding. Alloy creep rates of 10-7-10-6 s-1 were measured contrasting with 10-5-10-4 s-1 for the ZrB2-SiC composite approaching the design creep rate of 10-8s-1 for long duty cycle aerospace applications. | |
| dc.description.department | Mechanical Engineering, Department of | |
| dc.format.digitalOrigin | born digital | |
| dc.format.mimetype | application/pdf | |
| dc.identifier.uri | http://hdl.handle.net/10657/1196 | |
| dc.language.iso | eng | |
| dc.rights | The author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s). | |
| dc.subject | UHTC | |
| dc.subject | Extreme Environment | |
| dc.subject | Diboride | |
| dc.subject | Creep | |
| dc.subject | Fracture behavior | |
| dc.subject | Alloy | |
| dc.subject | Composites | |
| dc.subject | Ceramic | |
| dc.title | Creep Behavior of a Zirconium Diboride-Silicon Carbide Composite and Preliminary ZrB2-WC Quasi-Binary Alloy Development for Long Duty Cycle Aerosurfaces and Structural Propulsion Applications | |
| dc.type.dcmi | Text | |
| dc.type.genre | Thesis | |
| thesis.degree.college | Cullen College of Engineering | |
| thesis.degree.department | Mechanical Engineering, Department of | |
| thesis.degree.discipline | Materials Engineering | |
| thesis.degree.grantor | University of Houston | |
| thesis.degree.level | Doctoral | |
| thesis.degree.name | Doctor of Philosophy |