Development of iron-base long-range ordered (LRO) alloys for fusion reactor first wall and blanket applications

Iron-base LRO alloys with base compositions (Fe,Ni)₃V are being developed for fusion reactor applications. The phase relationships in the LRO alloys depend strongly on the nickel concentration in the range of 31 to 40%. The a phase field existing in the low nickel alloys at temperatures above their critical ordering temperature (T_c), can be eliminated by increasing nickel content to 40%. Tensile tests as a function of temperature indicate that the LRO alloys have superior high-temperature strength. Unlike conventional alloys, the yield strength of the LRO alloys increases with temperature and reaches a maximum around T_c. Titanium additions (<1%) improve the ductility of the LRO alloys at elevated temperatures. The alloys show excellent creep resistance and structural stability. Long-term aging at 550°C does not cause any significant change in tensile properties. The formation of long-range order lowers the creep rate by more than two orders of magnitude. © 1981.