Analysis of the mechanical behaviour of materials through the 2nd and 3rd order stress determination

Abstract
Based on the shift of the Bragg reflection and its broadening, 1st and 3rd order internal stresses in crystalline materials can be determined respectively by diffraction method. Between these two orders, we can define a mesoscopic scale, where the stresses come from different arrangements of dislocation arrays or grain misorientation in a polycrystal. For all materials, three orders internal stressescan be found simultaneously. The first application presented here is on an eutectoïd steel with 12% in volume of cementite. The 1st and 2nd order internal stresses have been determined in each phase, especially in cementite phase using a high intensity synchrotron beam. The second example concerns a cold-rolled pure Aluminum where the 2nd and 3rd order internal stresses are present at the same time. With the high resolution synchrotron diffraction, the analysis of peak asymmetry can be used to relate internal stresses with dislocation arrangements during plastic deformation.