Wu, Jinghui
(2005)
DEVELOPMENT OF A NEW TECHNIQUE TO IDENTIFY AND QUANTIFY COMPLEX AUSTENITE DECOMPOSITION PRODUCTS.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Polycrystalline aggregates are comprised of three microstructural features: grain centers, grain boundaries, and regions affected by grain boundaries. It is these features that determine the mechanical properties, and any advanced understanding of microstructure-property relations requires their quantitative description. Traditionally, descriptions of microstructures have been based on visualization, i.e., how grains appear in the optical or scanning electron microscope (SEM). While this may lead to classification systems that permit differentiation, it does not allow for quantification, especially in complex microstructures, and does not lend itself to either developing or applying structure-property relationships. The goal of this study is to present a new approach to the characterization of complex microstructures, especially those found in advanced modern high strength steels. For such steels, the new approach employs the fact that different austenite decomposition products formed at different transformation temperatures have different dislocation or sub-grain boundary densities. Hence, measuring the degree of lattice imperfection of the grain centers of the ferrite is one way of first identifying, then grouping, and finally quantifying, the different types or forms of ferrite. The index chosen in this study to distinguish the degree of lattice imperfection is the image quality (IQ). As part of the new approach a procedure has been developed to improve the accuracy of applying IQ measurements. This procedure includes three major features: IQ normalization, Grain Boundary Region (GBR) identification and the Multi-Peak model. These three features make this new approach a unique technique, which quantitatively describes the complex microstructures with much more details. The potential application of this technique and further development has also been discussed at the end of this study.
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Details
| Item Type: |
University of Pittsburgh ETD
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| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
14 October 2005 |
| Date Type: |
Completion |
| Defense Date: |
17 November 2004 |
| Approval Date: |
14 October 2005 |
| Submission Date: |
9 March 2005 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Materials Science and Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
diffraction pattern; EBSD; ferrite; grain boundary; image quality; lattice imperfection; microstructure; phase identification |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-03092005-172439/, etd-03092005-172439 |
| Date Deposited: |
10 Nov 2011 19:32 |
| Last Modified: |
15 Nov 2016 13:36 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/6464 |
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