MICROSTRUCTURAL EVOLUTION OF A HIGH CR FE-BASED ODS ALLOY BY DIFFERENT COOLING RATES

• Published in: Nuclear engineering and technology Vol. 40; no. 2; pp. 99 - 106
• Main Authors: Shen, Yin-Zhong, Cho, Hae-Dong, Jang, Jin-Sung
• Format: Journal Article
• Language: Korean
• Published: 2008
• Subjects: Tensile Strength; Cooling Rate; ODS Alloy; Microstructure
• ISSN: 1738-5733; 2234-358X

Through mechanical alloying, hot isostatic pressing and hot rolling, a 9%Cr Fe-based oxide dispersion-strengthened alloy sample was fabricated. The tensile strength of the alloy is significantly improved when the microstructure is modified during the post-consolidation process. The alloy samples were strengthened as the cooling rates increased, though the elongation was somewhat reduced. With a cooling rate of $800^{\circ}C/s$ after normalization at $1150^{\circ}C$, the alloy sample showed a tensile strength of 1450 MPa, which is about twice that of the hot rolled sample; however, at $600^{\circ}C$ the tensile strength dramatically decreased to 620 MPa. Optical microscope and transmission electron microscope were used to investigate the microstructural changes of the specimens. The resultant strengthening of the alloy sample could be mainly attributed to the interstitially dissolved nitrogen, the fraction of the tempered martensite, the fine grain and the presence of a smaller precipitate. The decrease in the tensile strength was mainly caused by the precipitation of vanadium-rich nitride.