Use of Positron Annihilation Spectroscopy for Stress-Strain Measurements: Quarterly Progress Report (March – May 2005)

Accomplishments: ● Analyses of defects (dislocations) in martensitic Alloy EP-823, cold-reduced to different levels, have been performed by using transmission electron microscopy. The dislocation density has been related to the degree of cold-reduction and residual stress in terms of a line-shape parameter determined by the positron annihilation spectroscopy (PAS). ● Additional PAS measurements are ongoing on tensile, welded and cold-worked specimens of Alloys EP-823 and HT-9 at the Idaho Accelerator Center of ISU. Both Subhra and Silpa are involved in these measurements. ● Silpa is performing neutron diffraction (ND) measurements at the Atomic Energy of Canada Limited (AECL), Chalk River Laboratory using Cold-worked and welded specimens of Alloys EP-823 and HT- 9. ● TEM studies involving welded specimens of Type 304L stainless steel and Alloy EP-823 are being performed by Srinivas to characterize defects at the fusion line, heat-affected-zone and base metal