Microstructural Transformations of Austenitic Stainless Steels under Ga Ion Irradiation
poster presentation: Monday 2010-08-23 05:00 PM - 07:00 PM in section Focused ion beams, ion lithography
Last modified: 2010-06-02
Abstract
In the last decade Focussed Ion Beam (FIB) milling has become an important tool for the preparation of TEM and atom-probe specimens. Although sample milling is the objective, ion implantation is an unavoidable by-product. Ga ions with energies of 2, 5, and 30keV were implanted in 304 stainless steel during sample preparation and Electron Backscatter Diffraction (EBSD) mapping was performed prior and post irradiation. It was found that the austenitic steel (fcc) locally transforms to bcc at selected grain orientations when a critical dose was reached. Molecular Dynamics (MD) ion range simulations [1] were used to reveal that the penetration depth of the Ga ions varies significantly depending on the crystallographic orientation. For those orientations that do not promote channelling and favour Ga ion accumulation near the sample surface, the transformation can be explained due to the increased internal stresses induced and the change in local composition. These results suggest that it is possible to modify the crystal structure of the surface layer of austenitic steels in a controlled manner. They also show that extra care should be taken when analyzing EBSD results.
[1] K Nordlund, Molecular dynamics simulation of ion ranges in the 1-100 keV energy range, Comp Mat Sci 3, (1995) 448 - 456
Author(s) affiliation:
Mageshwaran Ramesh, Laboratory for Nuclear Materials, Nuclear Energy and Safety Research Department, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland, Switzerland
Kai Nordlund, Accelerator Laboratory, University of Helsinki, P.O. BOX 43, FIN-00014, Finland, Finland
T Ben Britton, Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK, United Kingdom
Sergei L Dudarev, Culham Centre for Fusion Energy (CCFE), Abingdon, Oxfordshire, OX14 3DB, UK, United Kingdom
David W Saxey, Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK, United Kingdom
George D W Smith, Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK, United Kingdom
Sergio Lozano-Perez, Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK, United Kingdom
*presenting author