Residual stress depth profiling using grazing incidence x-ray diffraction

Residual stresses are usually unavoidable in surface layers of surface-treated materials. Mechanical processes such as grinding, machining and polishing are commonly used surface treatments in the manufacture of the ceramic components and can constitute up to 90% of the production cost of the component. Even in the most carefully executed processes the surface damage is often unavoidable and causes residual stress in the surface layers. The stresses introduced, both compressive and tensile affect the mechanical properties and durability of the structures involved. These residual stresses however, are not easily modeled because of the complexity of the surface treatments and different reactions of materials to the treatments. Thus the measurements of residual stress are still essential for advancing the understanding of the surface treatments.; In this study the grazing incidence x-ray diffraction method is characterized and employed to obtain the depth profiles of the residual stresses on ground and polished surfaces of an {dollar}rm Alsb2Osb3{dollar}/SiC(w) composite specimen. The effects of x-ray refraction on measured diffraction angles and x-ray penetration depth were studied. The effect of specimen displacement on the measurements was also assessed.; Because all physical quantities measured by x-ray diffraction are averaged over the x-ray irradiated volume and weighted by the absorption of x-rays in the material, they are therefore functions of {dollar}tau{dollar} the 1/e penetration depth ({dollar}tau{dollar}-profiles). However the z-profiles of these quantities (where z is the depth beneath the surface) are generally more desirable for understanding the residual stresses caused by a particular surface treatment. Numerical and analytical methods were used to determine the z-profiles from the experimentally determined {dollar}tau{dollar}-profiles. The inversion methods used were all characterized using known z-profile functions before applying them to the real data.; The residual stress profiles (both {dollar}tau{dollar} and z), in the alumina matrix phase in ground and in polished surfaces of the specimen are presented and compared.; It was found that the residual stresses are directly related to the damaged layer in the surface. On the ground surface the z-profile clearly showed a sub-surface maximum in the in-plane residual stress which was not evident in the {dollar}tau{dollar}-profile. The determination of such stress maxima non-destructively has important implications for sub-surface cracking and failure and for grinding/finishing protocols. The stress maximum was reduced and shifted as a result of polishing. {dollar}tau{dollar} and z depth profiles of residual strain and of lattice spacing were also obtained on sputtered Mo films and Cu(In{dollar}rmsb{lcub}1-x{rcub}Gasb{lcub}x{rcub})Sesb2{dollar} films respectively and have provided useful information for the fabrication of CIGS solar cells.; The depth profiling procedure, including the {dollar}tau{dollar}-profile inversion process, can be used to characterize depth profiles of any physical quantities that can be measured by x-ray diffraction.