In situ characterisation of welds by X-ray diffraction

Recent focus for the team has turned to stress and strain measurements using X-ray diffraction measurements as Dr Leigh Connor represented Diamond’s Industrial Liaison team at two conferences highlighting the strengths of applying synchrotron techniques to non-destructive, in situ characterisation of engineering materials.

Oxford played host to the seventh Size-Strain conference on “Diffraction Analysis of the Microstructure of Materials”. The conference, hosted by Diamond Light Source, took place at the University of Oxford’s Department of Engineering Science and focused on the analysis of materials microstructure and properties using X-ray diffraction methods. There was a particular focus on the application of diffraction techniques to polycrystalline materials, methodologies for the study of lattice defects, residual stress and texture in thin films, surfaces and nanostructures, and specific methods for the analysis and modelling of X-ray diffraction data for applications in materials science problems. The seventh conference in the series also included new topics and methods such as X-ray imaging and PDF (pair distribution function) analysis. The programme also included facility tours of both Diamond Light Source and ISIS, the neutron facility also based on the Rutherford Appleton site.

Dr Thomas Connolley, Senior Beamline Scientist, examines the high energy diffraction set up on I12.

Diamond Light Source

Dr Thomas Connolley, Senior Beamline Scientist on I12, examines the high energy diffraction set up

The second conference, MECASENS VIII is the 8^th International Conference on Mechanical Stress Evaluation by Neutron and Synchrotron Radiation and took place in Grenoble in France, hosted by the ESRF. Keynote speakers included Philip Withers, Ismail Cevdet Noyan and Martin Müller.

Themes of the conference included stress evaluation using neutrons, synchrotron radiation and X-rays; the development of measurement methods and instrumentation; material processing and residual stresses; the influence of residual stresses on physical and mechanical properties of materials and components; the measurement and assessment of residual microstresses and intergranular stresses; residual strains and stresses in complex materials, e.g. multiphase materials and biomaterials; residual stresses in thin films and microcomponents; industrial applications of residual stress analyses using neutrons, synchrotron radiation and X-rays; and complementary techniques for residual stress measurements.

In partnership with his collaborators from the Department of Materials Science and Metallurgy at University of Cambridge, IUT GMP de Nimes, Department of Materials, Imperial College and ISIS, Leigh presented his work on “In situ characterisation of the strain distribution produced around gas tungsten arc (GTAW) welds” based on high energy X-ray diffraction experiments performed at Diamond investigating the strain around a weld in situ.

In Leigh’s work, high energy synchrotron X-ray diffraction has been used in conjunction with spatially resolved pyrometry to determine the thermal and deviatoric strains distributions that exist around a weld in situ. Presenting at MECASENS in the processing and welding session, Leigh outlined the results of studies performed on welds made on ferritic and austenitic steels and discussed the relative merits of performing such experiments.