Irradiation Effects And Welding Behavior Of Materials For Nuclear Fusion Reactor

Controlled nuclear fusion reactor will be a new energy in the future, which is considered as infinite, clean and safe. The materials applied in the nuclear fusion reactor will be failure duo to the high energy neutron irradiation. Researchers usually used ions and electron irradiation instead of neutron irradiation to investigate the microstructures evalution, since the neutron irradiation experiments has a certain degree risk. A large number of studies illustrated that low activation ferritic/martensitic steel and oxide dispersion strengthened (ODS) alloys haveexcellentirradiation tolerance, and the irradiation tolerance can be improved by increasing the number density of grain boundaries and free surfaces in the materials. Irradiation effects of refined China low activation martensitic (R-CLAM) steel and ODS alloys were investigated in this paper, the weldability of the ODS alloys were also studied. Innovative achievements were stated as following:Ions and electron irradiation experiments were performed on R-CLAM steels. Ions irradiation results show that, the number density of the irradiation induced defects and irradiation hardening for the R-CLAM steel is reduced compared to the bulk CLAM steel. This is attributed to the higher number density of gain boundaries in the R-CLAM steel can act as sink for irradiation induced defects. The diameter and number density of irradiation induced defects increase with increasing the irradiation dose. Nano-grains in the R-CLAM steel turned into martensitic duo the thermal spike during the ions irradiation, and a compressive stress formed in the irradiation layer, while a tensile stress in the martrix. The electron irradiation results showed that precipitates formed in the R-CLAM steel during the high temperature electron irradiation.Friction stir welding technique was successfully performed on the ODS copper alloy, a special "L"line formed in the welded joints. The micro-hardness along the weld cross-section shows "V" shape distribution and the hardness of stir zonehas the lowest values duo to the continuous dynamic recrystallization happened.Au ions irradiation at room temperature were perfomed on the ODS copper alloys, and the same irraidiaiton experiments were also performed on the pure copper, in order to investigate the interfaces between the nano-particles and matrixeffectsfor the irradiation tolerance. Compared with the irradiated pure copper, larger average diameter and lower number density of irradiation-induced dislocation-loops were detected in the ODS copper alloy, which reveals that large volume of Al2O3 particles existed in the ODS copper alloy can act as effective sinks for the irradiation-induced defects. Irradiation hardening in the ODS copper alloy is lower than that in the pure copper were also detected. In addition, the residual oxygen absorbed around the Al2O3 particles are stimulated and interacted with the matrix during the irradiation process, which results in some parts of the matrix oxidizing.Friction stir welding technique was successfully performed on the ODS steel. In the heat affected zone, slightly grian growth happened; equiaxed grain structure was achieved in the stir zone duo to the continuous dynamic recrystallization happened; the adivaced side of the thermo-mechanically affectedzone performed obvious plastic flow characteristics, while the retreating side was not.The diameter of the nano-particles in the welded joints was increased and the number density was reduced, especially in the advanved side of the thermo-mechanically affected zone. This is contributed to the friction and stack happened between different flowing layers in the advanved side of the thermo-mechanically affectedzone, the nano-particles collided with each other and then aggregated.The base metal, heat affected zone and the stir zone of the ODS steel were irradiated with Au ions at 500 ℃, the results show that, voids formed in the base metal and the heat affected zone, while in the stir zone, no voids were detected, which is ascribed to the high density of dislocations and grain boundaries can act as sink for irradiation induced defects in the stir zone. Irradiation hardening happened in the base metal and the heat affected zone, the irradiation hardening is much higher in the heat affected zone than that of the base metal. While in the stir zone, the hardening decreased after irradiation duo to the original dislocations recovery happened during the high temperature irradiation.