Quantitative characterization of microstructure in high strength microalloyed steels

• Author / Creator

  Li, Xiujun

• X-ray diffraction (XRD) profile fitting (Rietveld method) was used in this study to characterize the microstructure for seven microalloyed steels, which were produced through thermomechanical controlled processing (TMCP). Microstructure characterization was conducted through the strip thickness. The microstructural variables studied include subgrain size, dislocation density, texture index and weight percent of retained austenite. The subgrain size was also analyzed by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The effects of processing parameters, including coiling temperature, cooling rate and alloying elements, on the microstructure were also investigated. It was found that decreasing the coiling temperature resulted in a finer subgrain size and higher dislocation densities. The texture index was observed to increase with decreasing coiling temperature. The subgrain size decreased and dislocation density increased as the amount of alloying elements (Ni, Mo and Mn) were increased. The amount of retained austenite increased at the strip center with increasing coiling temperature and increasing C and Ni content.

• Subjects / Keywords

  • Texture
  • Cooling rate
  • Micro-structure
  • Subgrain size
  • Coiling temperature
  • EBSD
  • Dislocation density
  • Microalloyed steel
  • Rietveld method
  • Retained austenite
  • TMCP

• Graduation date

  Fall 2009

• Type of Item

  Thesis

• Degree

  Master of Science in Materials Engineering

• DOI

  https://doi.org/10.7939/R3VB02

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.