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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Strain Path Effect on Austenite Transformation and Ductility in TBF 1180 Steel

Gibbs, Parker Kenneth 01 March 2019 (has links)
TBF 1180 steel was studied under various conditions focusing on the correlation of ductility and amount of retained austenite. Samples were prepared from sheet stock and then strained using limiting dome height tooling (LDH), a standard uniaxial test frame, and a tensile stage for use in an electron microscope. The steel was observed in plane, biaxial, and uniaxial strain to determine its effect on retained austenite transformation and ultimately, ductility. Retained austenite was observed using a scanning electron microscope (SEM) equipped with an electron backscatter detector (EBSD) to distinguish the different phases present. Initial austenite levels were around 5% by volume and was quickly reduced as the sample was strained. The biaxial samples were the slowest to transform, having about 2.5% austenite at .05 effective strain, which allowed the specimen to reach an effective strain of .3 with 1.1% austenite remaining. In contrast, the plane strain samples had the fastest rate of transformation having only 1.2% austenite at .05 effective strain and .7% austenite at a final effective strain of .18. Both forms of uniaxial, (in-situ and ex-situ), were near identical, as expected, and exhibited an austenite transformation curve between that of the plane and biaxial curves. The uniaxial austenite level at .05 strain was 2.1% and was able to reach about .15 strain with a final austenite percentage around 1%. It was concluded that the biaxial strain path had the greatest ductility due in part to its slower austenite transformation rate while plane and uniaxial strain paths were not as ductile with their faster austenite transformation rates.

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