Stress determination with high lateral resolution using neutron diffraction

Determination of stress fields by neutron strain scanning provide a non-destructive method applicable in a broad variety of applications in materials science and engineering applications. The bandwidth reaches from measurements in bulk material of huge samples to high-resolution measurements normally at interfaces or surfaces. Although the gauge volume of neutron instrumentation is comparatively large, it is possible to perform high-resolution measurements at surfaces or interfaces. By introducing radial focusing collimators it is possible to reduce the surface error such that surface measurements are possible down to a few 10 μm from a surface. The strain scanning option of the D1A high-resolution powder diffractometer is equipped with radial collimators. It has been successfully used for measurements on coatings, medical implants, shot peened and laser shock peened surfaces. The paper describes the differences between collimating and slit optics for beam definition and an application on NiCrAlY-coatings on steel. (orig.)