Woodruff School of Mechanical Engineering
COE/Structural Mechanics Seminar
What can one do with electron backscatter diffraction? Illustration through case studies
Dr. Gwenaelle Proust
School of Civil Engineering, University of Sydney, Sydney NSW 2006, Australia
Thursday, January 24, 2013 at 3:00:00 PM
MRDC Building, Room 4211
Electron backscatter diffraction (EBSD) is a versatile technique that allows the characterisation of the microstructure of crystalline materials through the indexing of diffraction patterns created by the interaction of the electrons of the beam of an SEM with the surface of the studied material. By analysing the data collected, one can determine several microstructure features such as texture, grain size distribution, phase distribution, amount of deformation etc. The recent developments that this technique has seen have allowed the improvement of the collected information by decreasing the time of collection, increasing the resolution and coupling the technique with EDS. Some of these new developments will be presented through two case studies. Case study 1: Quantitative analysis of deformation twinning in hexagonal close-packed metals Plastic deformation in hexagonal close-packed metal is accommodated by different slip and twinning systems. The multiplicity of deformation mechanisms that can be activated and the dependence of their activation on loading conditions explain the observed asymmetry and anisotropy of the hardening behaviour and texture evolution. Using EBSD one can determine the different twinning modes that have contributed to deformation but also the volume fraction of material that has twinned. Additionally the contributions of primary (material that has twinned once) and secondary (material that has twinned twice) twinning can be uncoupled to enhance the understanding of the effect of twinning on hardening and texture evolution. Case study 2: Microstructural Evolution of Stainless Steel after surface treatments Surface Mechanical Attrition Treatment (SMAT) is a treatment that enhances the mechanical properties of the material surface by creating a thin nanocrytalline layer. This treatment was applied to a 316L stainless steel to improve its wear and friction properties. Further to this SMAT treatment, some specimens were heat treated to 425˚C to test the stability of the nanocrystalline layer and others underwent a plasma nitriding process to further enhance their surface properties. Using EBSD, we were able to characterise the microstructural evolution of the stainless steel after these different treatments. However, several obstacles were encountered during the characterisation process such as sample preparation since we were interested to study a thin layer on the surface of the specimens and the resolution of the EBSD system since we were looking at nanosized grains.
Dr Gwenaelle Proust is a senior lecturer in the school of Civil Engineering at the University of Sydney. Her research interests focus on the relationships between microstructure and properties of materials, with particular emphasis on metals. She specialises in characterisation techniques, in particular electron backscatter diffraction, to study materials microstructures and in crystal plasticity modelling to predict the mechanical behaviour of metals.
Refreshments will be served.