Medium-manganese steels (5-12 wt%) are candidates for third-generation advanced high strength steel (AHSS). Potential applications for these steels are centered around the automotive industry due to their combination of high tensile strength, high tensile ductility, and low alloying cost. Previous studies at VT have been primarily focused on the effect of chemistry on mechanical properties with only a minor emphasis on microstructure. This led to a detailed investigation into the effect of carbon content on the microstructure of Fe8Mn2AlSiC alloys. Six different chemistries with carbon contents of 0.30, 0.34, 0.39, 0.44, 0.49 and 0.52 wt% were produced at the Kroehling Advanced Materials Foundry. After a variety of heat treatments, the samples were characterized using x-ray diffraction (XRD), electron backscatter diffraction (EBSD), electron probe microanalysis (EPMA), optical microscopy, and hardness testing. This thesis will discuss how the microstructure and hardness of these medium manganese steels is influenced by the carbon content. / Master of Science / This research will be used to help design steel alloys that might one day be used in automotive applications. These steels need to be tough and ductile so they can absorb impact without fracturing. This is especially important in the event of a car crash, in which the steel needs to deform without breaking and causing injury to the driver or passenger. In order to achieve such qualities today, expensive elements are often added to the steel which increases cost. Medium manganese steels hope to alleviate this issue by providing a less expensive alternative with similar deformation properties.
The properties of steel can be correlated with its microstructure, and more specifically, the different phases that make up the microstructure. These phases give rise to the macroscopic properties that make steel so useful. Microstructure can be controlled through chemistry and through thermomechanical processes. This research focuses on the effects of carbon and on heat treatments. This research is unique in that it keeps the chemistry consistent between all of the samples, making the effect of carbon or of the heat treatment identifiable. A total of six different carbon contents were tested over eight different heat treatment conditions.
After creating the samples, the hardness was measured. The samples were then characterized to understand the microstructure. The results of this research showed there is a direct connection between heat treatment and chemistry to the microstructure.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/118615 |
| Date | 03 April 2024 |
| Creators | Kalil, Andrew Jeffrey |
| Contributors | Materials Science and Engineering, Druschitz, Alan P., Reynolds, William T., Murayama, Mitsuhiro |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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