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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

Effects of alloying elements upon austenite decomposition in high strength low alloy steels

Chen, Jhewn-Kuang 10 October 2009 (has links)
The kinetics of austenite decomposition were studied in high purity Fe-0.1 C-0.4 Mn-0.3 Si-X (concentrations in weight percent, X represents 3 Ni, 1 Cr, or 0.5 Mo) steels at temperatures between 500 and 675°C. The transformation stasis phenomenon was found in the Fe-C-Mn-Si-Mo and Fe-C-Mn-Si-Ni alloys isothermally transformed at 650°C and 675°C but not in the Fe-C-Mn-Si and Fe-C-Mn-Si-Cr alloys at any of the temperatures investigated. The occurrence of transformation stasis was explained by synergistic interactions among alloying elements. The paraequilibrium model was applied to calculate the metastable fraction of ferrite in each alloy. This fraction was shown to coincide with cessation of transformation in the Mo alloy transformed at 600°C. Transformation stasis was found in both the Ni and the Mo alloys isothermally reacted at 650°C and 675°C. The interactions among Mn, Si, and Mo as well as interactions among Mn, Si, and Ni appear to decrease the threshold concentrations for occurrence of transformation stasis in Fe-C-Mn-Si systems. The segregation of Mn and Mo to the α/γ boundary assisted by Si was suggested to enhance the drag force and led to transformation stasis. In the Ni alloy, lower driving force for ferite formation by addition of Ni could be responsible for occurrence of transformation stasis. / Master of Science

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