Characterization of Residual Stresses in Structural Materials for Nuclear Applications

Residual stresses may be generated in target structural material used in accelerator-driven transmutation due to plastic deformation. Nondestructive positron annihilation spectroscopic (PAS) method has been used to estimate residual stresses in candidate structural materials such as martensitic Alloy EP-823 and Alloy HT-9. Different line shape parameters (S, W & T) obtained from the PAS measurements have been related to the degree of cold deformation. The results indicate that the magnitude of S parameter was enhanced at the intermediate level of cold deformation followed by an almost identical S value at the highest level of cold reduction. Conversely, the T parameter was reduced at higher level of cold deformation. The evaluation of the cold-worked specimens by transmission electron microscopy revealed the presence of dislocations, as expected.