E-Thesis 207 views 72 downloads
The combination of processes influencing fracture in ferritic steels. / Owen Williams
Swansea University Author: Owen Williams
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Abstract
In order to understand the brittle fracture of ferritic steels, it is necessary to understand all of the processes that have an influence on the brittle fracture. Much work has been done previously on grain boundary geometry and structure, grain boundary segregation, the effects of heat treatments a...
| Published: |
2003
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa42421 |
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| Abstract: |
In order to understand the brittle fracture of ferritic steels, it is necessary to understand all of the processes that have an influence on the brittle fracture. Much work has been done previously on grain boundary geometry and structure, grain boundary segregation, the effects of heat treatments and the fracture process, but little work has been reported on the combined result of these processes and the effects that they have on each other and the process of brittle fracture in ferritic steels. The aim of this project was to investigate the combined influence that the processes of grain boundary structure, segregation, and heat treatment have on the brittle fracture of ferritic steel. All experiments were carried out on a Fe-0.06wt%P-0.002wt%C and a Fe-0.12wt%P-0.002wt%C alloy, which was subject to a set of specific heat treatments. Investigations were made into the grain boundary structure of the material using Electron Back-Scatter Diffraction (EBSD) and the segregation studied by Auger Electron Microscopy (AES). A number of innovative analysis techniques were developed during the course of the program in order to determine the combined effects of boundary structure and segregation on the fracture process of the material. Two separate grain growth mechanisms were found to be operating in this material at different temperature ranges. Abnormal grain growth being prolific in this material at annealing temperatures above 900°C, normal grain growth being the dominant grain growth mechanism for annealing temperatures of below 900°C. Both abnormal grain growth and Sigma3 proportions were found to be dependent on the annealing temperature and both were affected by a transition that occurs at 0.65-0.75 of the melting temperature, given by (Tp) It was also found that 3at% more segregated phosphorus was present on {lcub}112{rcub} boundary planes than on {lcub}110{rcub} boundary planes on the fracture surfaces of the material. |
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| Keywords: |
Materials science. |
| College: |
Faculty of Science and Engineering |