300 mm ROLE OF GRAIN BOUNDARY CHARACTER ON DYNAMIC RECRYSTALLIZATIONMegan Frary, Boise State University, DMR 0642363 OVERVIEW RESULTS Dynamic recrystallization (DRX) occurs when low to medium stacking fault energy materials undergo deformation at high homologous temperatures (e.g., as seen during hot working). The objective of the project is to better understand the role of grain boundary character on dynamic recrystallization, both locally (e.g., through nucleation at individual triple junctions) and globally (e.g., when the fraction of special boundaries changes). A combination of experiments and computer simulations are being used to study the role of grain boundaries on DRX. APPROACH EXPERIMENTAL: High temperature mechanical testing will be performed on nickel, nickel-based superalloys and stainless steel alloys. Grain boundary engineering creates microstructures with different grain boundary character distributions and electron backscatter diffraction (EBSD) is used to map grain orientations and grain boundary misorientations over large areas. BSU will install the new MTS mechanical testing frame in Oct. 2007 for this work. COMPUTATIONAL: Monte Carlo simulations are being developed to study the effects of changing the fraction of twin boundaries on the kinetics and flow behavior in DRX. Experimentally-determined microstructures are used as the initial structure for the model. EBSD map showing how grain boundary engineering of Inconel 617 has increased the fraction of S3 (twin) boundaries from 46% to over 60%. In the figure above, red lines indicate S3 boundaries. Different colors correspond to different crystallographic orientations.
ROLE OF GRAIN BOUNDARY CHARACTER ON DYNAMIC RECRYSTALLIZATIONMegan Frary, Boise State University, DMR 0642363 In the past six months, one graduate student and four undergraduate students have been involved in the project. The PI, advisor to the MSE Club, is also working with club members to develop outreach programming for local high schools. Undergraduate students Master of Science students BEN ALBISTON, a sophomore in MSE, has been working on grain boundary engineering of stainless steel to create samples with different initial microstructures for mechanical testing. JARED STEIN is a first year graduate student in Materials Science and Engineering working toward a M.S. degree. Jared is developing Monte Carlo simulations to study dynamic recrystallization and the role that grain boundary character plays during deformation. WADE LANNING, a junior in MSE, joined the group in the spring of 2007. He is using object oriented finite element (OOF) programs to study thermal and mechanical stresses in polycrystalline materials. Visiting students SHARLA HOPKINS, a junior in MSE, joined the group in the fall of 2006. She spent this summer in Washington State’s REU program. She is doing microstructural engineering of nickel-based superalloys for mechanical testing. MICHAEL CARROLL, a senior in MSE at Washington State University, spent the summer at Boise State University characterizing grain boundary networks using EBSD.