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Precipitation Sensitivity to Alloy Composition in Fe-Cr-Mn Austenitic Steels Developed for Reduced Activation for Fusion Application

出版	ASTM International, 1990
URL	http://books.google.com.hk/books?id=ooR7zgEACAAJ&hl=&source=gbs_api

註釋Special austenitic steels are being designed in which alloying elements like molybdenum, niobium, and nickel are replaced with manganese, tungsten, vanadium, titanium, and/or tantalum to reduce the long-term radioactivity induced by fusion reactor irradiation. However, the new steels still need to have properties otherwise similar to commercial steels like Type 316. Precipitation strongly affects strength and radiation-resistance in austenitic steels during irradiation at 400 to 600°C, and precipitation is also usually quite sensitive to alloy composition. The initial stage of development was to define a base Fe-Cr-Mn-C composition that formed stable austenite after annealing and cold-working, and resisted recovery or excessive formation of coarse carbide and intermetallic phases during elevated temperature annealing. These studies produced a Fe-12Cr-20Mn-0.25C base alloy. The next stage was to add the minor alloying elements titanium, vanadium, phosphorous, and boron for more strength and radiation-resistance. One of the goals was to produce fine MC precipitation behavior similar to the Ti-modified Fe-Cr-Ni prime candidate alloy (PCA). Additions of Ti + V + P + B produced fine MC precipitation along network dislocations and recovery/re-crystallization resistance in 20% cold-worked material aged at 800° for 168 h, whereas tungsten, titanium, W + Ti, or Ti + P + B additions did not. Addition of W +Ti + V + P + B also produced fine MC, but caused some ? phase formation and more recrystallization as well. These new alloys, therefore, achieved several of the initial design goals. Their fine MC precipitation and recovery/recrystallization behavior during aging is similar to that of the PCA. Calculations show that the new steels have over 103 times less long-term radioactivity than Type 316.