Analysis of the residual stress in zirconium subjected to surface severe plastic deformation

The residual stress of commercially pure zirconium specimens subjected to surface mechanical attrition treatment (SMAT) for different durations is measured with X-ray diffraction (XRD). XRD peak broadening analysis is conducted to obtain the distributions of the crystallite size, microstrain and dislocation density as functions of the depth from the processed surface. Finite element modeling is performed to reveal the characteristics of the residual stress distribution. Microstructure observation using optical and electron microscopy are also carried out in order to elucidate the residual stress development. The correlations between the microstructure features and the residual stress distribution in zirconium are examined. The results indicate that a more pronounced compressive residual stress field can be generated by the SMAT process compared to that obtained by conventional shot peening, and that the compressive residual stress distributions exhibit nonlinear variation with the distributions of the full width at the half maximum of the XRD profiles and the dislocation densities.