  A decrease of fracture toughness of irradiated materials is usually observed,
as reported for austenitic stainless steels in Light Water Reactors (LWRs) or
copper alloys for fusion applications. For a wide range of applications (e.g.
structural steels irradiated at low homologous temperature), void growth and
coalescence fracture mechanism has been shown to be still predominant. As a
consequence, a comprehensive study of the effects of irradiation-induced
hardening mechanisms on void growth and coalescence in irradiated materials is
required. The effects of irradiation on ductile fracture mechanisms - void
growth to coalescence - are assessed in this study based on model experiments.
Pure copper thin tensile samples have been irradiated with protons up to 0.01
dpa. Micron-scale holes drilled through the thickness of these samples
subjected to uniaxial loading conditions allow a detailed description of void
growth and coalescence. In this study, experimental data show that physical
mechanisms of micron-scale void growth and coalescence are similar between the
unirradiated and irradiated copper. However, an acceleration of void growth is
observed in the later case, resulting in earlier coalescence, which is
consistent with the decrease of fracture toughness reported in irradiated
materials. These results are qualitatively reproduced with numerical
simulations accounting for irradiation macroscopic hardening and decrease of
strain-hardening capability.
