Application of micro-indentation to irradiated alumina and vanadium/alumina joints

The micro-indentation test as a method to introduce interface crack and to investigate the bonding strength of metal/ceramics joints is examined. Micro-indentation test was carried out using Vickers hardness tester at room temperature on joints of poly- or single-crystal alumina and vanadium or vanadium alloys. The vanadium/alumina (V/Al2O3) joints, unirradiated and irradiated in FFTF/MOTA in a helium-filled capsule at 693 K, were tested. The irradiation damage of the joint was about 40 dpa. Micro-indentation on the unirradiated joint interface showed several types of deformation and crack propagation behavior depending on the bonding strength of the joints. Irradiation hardening and brittle behavior were observed on the alumina side of the irradiated V/Al2O3 joints. Results of micro-indentation test at the V/Al2O3 interface showed the possibility of irradiation-induced strengthening of the interface caused by irradiation-induced mixing at the interface.