Mechanical property changes and microstructures of dispersion-strengthened copper alloys after neutron irradiation at 411, 414, and 529°C

Dispersion-strengthened copper alloys have shown promise for certain high heat flux applications in both near-term and long-term fusion devices. This study examines mechanical properties changes and microstructural evolution in several oxide dispersion-strengthened alloys which were subjected to high levels of irradiation-induced displacement damage. Irradiations were carried out in the fast flux test facility (FFTF) to 34 and 50 dpa at 411 to 414°C and 32 dpa at 529°C. The alloys include several oxide dispersion-strengthened alloys based on the Cu-Al system, as well as ones based on the Cu-Cr and Cu-Hf systems. Of this group, certain of the Cu-Al alloys, those produced by an internal oxidation technique to contain alumina weight fractions of 0.15 to 0.25%, outperformed the other alloys in all respects. These alloys, designated CuAl15, CuAl20, and CuAl25, were found to be resistant to void swelling up to 50 dpa at 414°C and to retain their superior mechanical and physical properties after extended irradiation. The major factor which controls the stability during irradiation was found to be the dispersoid volume fraction and distribution. The other alloys examined were less resistant to radiation-induced properties changes for a variety of reasons. Some of these include dispersoid redistribution by ballistic resolution, effects of retained dissolved oxygen, and nonuniformity of dispersoid distribution. The effect of laser welding was also examined. This joining technique was found to be unacceptable since it destroys the dispersoid distribution and thereby the resistance of the alloys to radiation-induced damage.