Strain field and scattered intensity profiling with energy dispersive x-ray scattering

Abstract

Two powerful synchrotron x-ray scattering techniques for residual strain depth-profiling and tomography-like scatter-intensity profiling of materials are presented. The techniques utilize energy dispersive x-ray scattering, from a fixed microvolume, with microscanning of the specimen being used to profile its interior. The tomography-like profiles exploit scattering-cross-section variations, and can be contrast enhanced by separately monitoring scattering from different crystal structures. The strain profiling technique is shown to finely chronicle the internal strain variation over several mm of steel. Detailed strain profiling for a cantilever spring demonstrates the interplay of residual and external stresses in elastic/plastic deformation. Since surface compression, by shot peening, is a classic method to fortify against fatigue failure, the strain profile for a shot-peened, surface-toughened material is determined and discussed in terms of a simple elastic–plastic stress/strain model. Finally the lattice strains in a WC/Co coated steel composite material are discussed.