Void growth and coalescence in irradiated copper under deformation

TL;DR

This study investigates how irradiation affects void growth and coalescence in copper, revealing accelerated void growth and earlier coalescence in irradiated samples, which correlates with decreased fracture toughness.

Contribution

It provides experimental and numerical insights into how irradiation-induced hardening influences ductile fracture mechanisms in copper.

Findings

Irradiation accelerates void growth in copper.

Void growth mechanisms are similar in irradiated and unirradiated copper.

Earlier coalescence occurs in irradiated copper, reducing fracture toughness.

Abstract

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.