Spinodal-like decomposition of Fe-35Ni and Fe-Cr-35Ni alloys during irradiation or thermal aging

Fe-35Ni and Fe-Cr-35Ni alloys appear to thermally decompose in a spinodal-like but very sluggish manner at temperatures between ∼400 to 800 C, with the miscibility gap spanning nickel levels of ∼30 to 40%. When irradiated with either charged particles or neutrons at these temperatures, the instability is accelerated and the miscibility gap widens to span ∼25 to 50% Ni, developing very large and temperature-dependent wavelengths. This phenomenon is thought to be the result of the combined action of a natural instability and radiation-induced segregation, cooperating to produce a new form of compositional self-organization. Three experimental methods have been developed to allow a visualization of the decomposition on a large scale. (orig.)