Heavy-ion irradiation and post-irradiation annealing effects in explosion-welded CuCrZr/316LN joints for ITER application

Abstract

Bimetallic plates of CuCrZr/316LN are important heat sink components in the ITER first wall. Their in-reactor performance was investigated with 6.4 MeV Fe3+ ion irradiation (500 °C/10.5 dpa), as an analogue for neutron damage. Detailed characterizations showed that the CuCrZr/316LN joints have maintained good structural integrity after irradiation. The as-irradiated interface consisted of a nanocrystalline interlayer, typically of <1 μm in width, mixed of CuCrZr and 316LN grains measuring 20–250 nm in size. Black-spots and loop/loop rafts dominated the damage microstructure on 316LN and CuCrZr sides of the interface, respectively. A series of 30 min long post-irradiation annealing experiments saw the onset of interlayer evolution in CuCrZr/316LN joints at 400 °C by grain boundary motion and Ostwald ripening, and further acceleration at ≥600 °C. Structural collapse of the interlayer is expected at extended time scales. Finally, a brief comparison between heavy-ion and neutron irradiation damage (Yi et al. 2021) in CuCrZr/316LN joints is made, with regard to defect production and interfacial transport behaviour of chemical elements.