<p>Thirty-two specimens provided by EPRI were tested by thermoelectric and magnetic nondestructive characterization techniques in this study.&nbsp; These specimens were made of four types of austenitic stainless steel plate material (SS-304, SS-316, SS-347, and SS-A286) that were first cold-rolled in a range of 0%-80% thickness reduction to simulate increasing dislocation density associated with fast neutron irradiation embrittlement and were subsequently machined into 0.5”-thick compact tension (CT) specimens.&nbsp; These specimens were characterized by two thermoelectric NDE techniques, namely a commercially available two-point thermoelectric alloy sorter and a custom-built high-precision automated four-point thermoelectric power (TEP) measurement system.&nbsp; The first technique allowed highly localized “hot-spot” measurements with good spatial resolution even on these relatively small CT specimens, while the second technique offered higher repeatability and absolute accuracy.&nbsp; Both types of thermoelectric measurement indicated the same basic patterns of changing TEP with cold work.&nbsp; The two austenitic stainless steel alloys that were known to undergo significant martensitic phase transformation during low-temperature plastic deformation, namely SS-304 and SS-347, exhibited strong increase in TEP with increasing cold work, while the other two alloys that are not susceptible to martensitic phase transformation due to plastic deformation, namely SS-316 and SS-A286, exhibited relatively weak decrease in TEP with increasing cold work.&nbsp; Since it is well known that martensitic phase transformation causes a significant increase of magnetic susceptibility in otherwise weakly paramagnetic austenitic stainless steels, magnetic susceptibility measurements were also conducted on the cold-worked specimens.&nbsp; It was found that the observed changes in TEP and magnetic susceptibility induced by cold work were closely related to each and, in the cases of SS-304 and SS-347 that exhibited strongly increasing TEP with increasing cold work, martensitic phase transformation likely dominated the observed pattern of TEP versus cold work.</p>

Thermoelectric Nde for Characterization of Fracture Properties of Mechanically Embrittled Austenitic Stainless Steel

Paper Proceedings: https://asmedigitalcollection.asme.org/qnde/QNDE2021/volume/85529

ASME 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE2021)

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