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

Abstract

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.