Neutron strain scanning on bimetallic tubes

Neutron diffraction measurements have been carried out on the REST diffractometer (Studsvik) on curved components fabricated by cold working bimetallic tubes. The tubes consist of two layers (an outer one of austenitic steel and an inner one of ferritic steel) with a total wall thickness of 6 mm. Both austenitic and ferritic components have been scanned at different positions, throughout the material thickness and for three orientations of the component axes with respect to the neutron momentum transfer vector. Due to the complicated geometry of the problem, Bragg peak data have been corrected for non-uniform illumination of gauge volume, neutron absorption and instrumental effects by means of a Monte Carlo simulation code which incorporates details of the diffractometer and a realistic model of the specimen. We report on estimates of the stress tensor components.