Sensitivity of thermo-electric power measurements to α–α′ phase separation in Cr-rich oxide dispersion strengthened steels
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The sensitivity of thermo-electric power (TEP) measurement to detect the undesired α–α′ phase separation occurring in Cr-rich oxide dispersion strengthened steels was investigated. TEP values were found to increase with time of exposure to 475 °C—the maximum temperature of the miscibility gap in Fe–Cr alloys. Exposure to 650 °C did not induce any changes in the TEP value. By examining the bend contours in dark-field TEM images, α′ precipitates were evidenced in aged PM2000. Using the Fe–XCr–YAl model alloys and X-ray photoelectron spectroscopy, the changes in TEP were traced back to the depletion of Cr from the matrix, caused by the formation of the Cr-rich α′ phase. By quantifying the effect of Cr content on the TEP value of model alloys, it was estimated that following 1000 h of aging, the Cr concentration in the α matrix of PM2000 alloy was reduced from 20 to ~13.5 at.%.
KeywordsDuplex Stainless Steel Oxide Dispersion Strengthened Oxide Dispersion Strengthened Alloy Oxide Dispersion Strengthened Steel Phonon Drag
The authors would like to thank Dr. Y. Gelbstein for performing the TEP measurements and Mr. O. Omassi for casting the model alloys. This study was supported by a dedicated collaboration agreement between the Israel Atomic Energy Commission and the Joint Research Centre of the European Commission.
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