Ambient and elevated temperature fracture and cyclic-fatigue properties in a series of Al-containing silicon carbides Page: 2 of 86
86 pagesView a full description of this thesis or dissertation.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
Abstract
Ambient and Elevated Temperature Fracture and Cyclic-Fatigue Properties of a Series of
Al-containing Silicon Carbides
By
Rong Yuan
Master of Science in Materials Science and Engineering
University of California, Berkeley
Professor R. O. Ritchie, Chair
Abstract -A series of in situ toughened, Al, B and C containing, silicon carbide
ceramics (ABC-SiC) has been examined with Al contents varying from 3 to 7 wt%. With
increasing Al additions, the grain morphology in the as-processed microstructures varied
from elongated to bimodal to equiaxed, with a change in the nature of the grain-boundary
film from amorphous to partially crystalline to fully crystalline. Fracture toughness and
cyclic fatigue tests on these microstructures revealed that although the 7 wt.% Al
containing material (7ABC) was extremely brittle, the 3 and particularly 5 wt.% Al
materials (3ABC and 5ABC, respectively) displayed excellent crack-growth resistance at
both ambient (25 C) and elevated (1300 C) temperatures. Indeed, no evidence of creep
damage, in the form of grain-boundary cavitation, was seen at temperatures at 1300 C or
below. The enhanced toughness of the higher Al-containing materials was associated
with extensive crack bridging from both interlocking grains (in 3ABC) and uncracked
ligaments (in 5ABC); in contrast, the 7ABC SiC showed no such bridging, concomitant
with a marked reduction in the volume fraction of elongated grains. Mechanistically,
cyclic fatigue-crack growth in 3ABC and 5ABC SiC involved the progressive
degradation of such bridging ligaments in the crack wake, with the difference in the1
Upcoming Pages
Here’s what’s next.
Search Inside
This document can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Thesis Or Dissertation.
Yuan, Rong. Ambient and elevated temperature fracture and cyclic-fatigue properties in a series of Al-containing silicon carbides, thesis or dissertation, August 30, 2004; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc787712/m1/2/: accessed July 17, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.