The 20th annual Symposium will be held on Thursday, April 23, 2009.

Quantifying the Influence of a 4.8-Tesla Magnetic Field on the α↔γ Phase Transitions in Fe-0.75C Steel
Norris 100, 10:00 AM

Ryan  Graham,   '09 7
   Major: Physics
   Hometown: Adrian, MI

Sponsor(s): Aaron Miller
Support: U.S. Department of Energy, Office of Science; Oak Ridge Science Semester, Oak Ridge National Laboratory, Oak Ridge Institute for Science and Education

Abstract: 
High magnetic fields are useful in materials processing but the influence that these fields have on the microscopic structure of the material is not well understood. Oak Ridge National Laboratory has developed the instrumentation to perform in-situ time-resolved neutron scattering experiments to better understand the effects that high magnetic fields have on the microscopic structure of alloys. Powder neutron diffraction data of an Fe-0.75C sample have been collected using this recently developed experimental apparatus. These Fe-0.75C data were analyzed to quantify the effect a magnetic field has on the body-centered cubic (a-Fe) to face-centered cubic (?-Fe) phase-transition temperatures of carbon steel. The data were collected at temperatures in the range with applied magnetic field strengths of 0 Tesla and 4.8 Tesla.

A multi-parameter least-squares fit to diffraction models was performed on the data to determine the volume fraction of a- and ?-Fe present. These data were used to construct diagrams of the Fe C steel’s a and ? phase volume fractions as a function of temperature at the two field strengths. These two diagrams were then compared in order to quantify the change in the transitions temperatures when the sample was exposed to the 4.8 Tesla field. This research has confirmed that a magnetic field increases the transition temperatures of the Fe-0.75C alloy and has provided quantitative information that will enable improved design and execution of future experiments to study the effects of thermo-magnetic processing.

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