X-ray micro Laue diffraction and neutron diffraction analysis of residual elastic strains in a 1% uniaxial tensile teste
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1137-EE10-28
X-ray micro Laue diffraction and neutron diffraction analysis of residual elastic strains in a 1% uniaxial tensile tested nickel alloy 600 sample Jing Chao1, Alison Mark2, Marina L. Suominen Fuller1, Rozaliya I. Barabash3, N. Stewart McIntyre1, Richard A. Holt2, Robert J. Klassen4, Wenjun Liu5 1
Department of Chemistry, University of Western Ontario, London, Ontario, Canada N6A 5B7
2
Nuclear Materials Group, Department of Mechanical and Materials Engineering, Queen’s University, Kingston Ontario, Canada K7L 3N6
3
Materials Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6118
4
Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ontario, Canada, N6A 5B9
5
Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois, USA 60439 ABSTRACT
The magnitude and distribution of elastic strain for a nickel alloy 600 (A600) sample that had been subjected to uniaxial tensile stress were measured by micro Laue diffraction (MLD) and neutron diffraction techniques. For a sample that had been dimensionally strained by 1%, both MLD and neutron diffraction data indicated that the global residual elastic strain was on the order of 10-4, however the micro-diffraction data indicated considerable grain-to-grain variability amongst individual components of the residual strain tensor. A more precise comparison was done by finding those grains in the MLD map that had appropriate oriented in the specific directions matching those used in the neutron measurements and the strains were found to agree within the uncertainty. Large variations in strain values across the grains were noted during the MLD measurements which are reflected in the uncertainties. This is a possible explanation for the large uncertainty in the average strains measured from multiple grains during neutron diffraction. INTRODUCTION Alloy 600 has been commonly used in nuclear steam generator tubing but it has proven to be susceptible to stress corrosion cracking (SCC) [1,2] The mechanisms of SCC involve interactions of chemical and mechanical factors, but highly localized uniaxial or biaxial strain is the key driving force. The study of strains that could lead to crack initiation requires diffraction techniques capable of measuring the direction and magnitude of (residual) elastic strains as well as the density and direction of dislocations that give rise to plastic deformation. Synchrotronbased Laue X-ray diffraction is a powerful method for such strain measurement. By combining high-brilliance X-ray sources, X-ray focusing optics and advanced reconstruction software, micro Laue diffraction (MLD) has emerged as an experimental technique capable of studying material microstructures and mechanical properties at a mesoscale (0.1-100µm). A non-
destructive 3-D X-ray crystal microscope based on Laue diffraction has recently been developed. This differential-aperture X-ray microscopy (DAXM) technique is capable of probing local crystal structure, grain orientation and strain
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