Mechanical properties of degraded OFE copper subjected to electron irradiation

Abstract

• SPT specimens of OFE copper are subjected to electron irradiation in accelerator. • Experimental results are used to get mechanical properties as a function of dose. • Fracture toughness indicates a sharp drop in ductility beyond 62.5 MGy. • Such observation is validated by variation of YS, biaxial-fracture-strain and specimen energy. • A New correlation between biaxial-fracture-strain and specimen energy is derived. The mechanical and fracture properties of aged materials degrade due to metallurgical and micro- structural changes during service life. Miniaturized specimen testing methodology has been evolved over the years to quantify such degradation mechanisms. Oxygen Free Electronic (OFE) Copper has wide applications in nuclear industry, particularly in fusion reactors and accelerators. Such material when subjected to nuclear irradiation during service life experiences degradation of ductility and fracture toughness. In the present study, linear accelerator is used to irradiate OFE Copper specimens up to varying dose of irradiation. Specimens are subjected to electron irradiation dose which varies from 11 MGy to 91.5 MGy. The specimens are then tested, and the load-displacement curves thus generated are used to quantify changes in mechanical and fracture properties, viz. yield stress, ultimate stress, specimen energy at fracture, bi-axial fracture strain and fracture initiation toughness of irradiated specimens. It is observed that there is a loss of ductility of OFE copper beyond 62.5 MGy irradiation dose as indicated by decrease in biaxial fracture strain, specimen energy and fracture initiation toughness. Such changes should be taken into consideration for calculating service life during the design of components made up of OFE Copper subjected to irradiation.