Microstructural Analysis Of Materials For Advanced Reactors Shanghai Jiao Tong University

In order to ensure the sustainable development of nuclear power, improve the safety of nuclear power, reliability, economics and nuclear non-proliferation, many countries have begun the work of the fourth-generation reactors investigation, and the most important feature of the fourth-generation reactors is the significant increasing of the operating temperatures. The higher operating temperature improves the thermo-electric conversion, the utilization of nuclear fuel and the economical efficiency of the power plant. Since the work environment of the reactors has become so demanding that the structural materials must have a more superior performance. The structural materials for the fourth-generation reactors should have oxidation resistance, creep resistance and excellent resistance to radiation. At present, seven materials have been selected as candidate structural materials for the fourth-generation reactors. They are nickel-based alloys, austenitic stainless steels, ferritic/martensitic steels, oxide dispersion strengthened steel, ceramic materials, refractory metals and graphite.In this paper, the candidate materials, the oxide dispersion strengthened steel PM2000 and the austenitic stainless steel 316L, have been selected for the experiments. PM2000 with hot-rolled and recrystallized condition, hot-rolled 316L, 316L with water-cooled, air-cooled, oil-cooled condition after a heat treatment at 1100℃and tensile fracture samples of 316L at 600℃and 650℃with a heat treatment at 1100℃and water-cooled condition have been made into samples for the experiments. TEM, EDX and OM have been used to analyze the microstructure of the two candidate materials. We have found that these precipitates have a size ranging from 10 ~ 50 nm, and Al-Fe(Cr) oxide, Al-Y(Fe ,Cr) oxide, Al(Cr,Ti) oxide and Fe-Cr(Al,Ti) intermetallic compounds, and Al-Fe(Cr) oxide is the first-found precipitates in PM2000 steel, compare the hot-rolled PM2000 and recrystallized PM2000, we found that precipitates in recrystallized samples are smaller than precipitates in hot-rolled samples. In the study of 316L, we have found that the grain growth and many twins in the matrix. And the phenomenon of serrated reduced until it disappears in the tensile test of 316L at 650℃should have something to do with the concentration of solute atoms.