Mechanical properties of 6H-SiC irradiated by neutron and MeV heavy ions: A nanoindentation and finite element method study

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Understanding the mechanical properties of structural materials under an irradiation environment stands as a major challenge for developing advanced nuclear systems. In this paper, the mechanical properties, including the Young's modulus, yield stress, and hardness, of SiC samples irradiated by neutron and heavy ions (3 MeV C and Si ions) have been investigated by nanoindentation measurement. When the load-depth curves were analyzed by the widely used Oliver-Pharr method, for the samples irradiated at the same displacement damage level (0.1 and 0.2 dpa), both the elastic modulus and hardness of the ion irradiated SiC are significantly higher compared with those of neutron irradiated samples. The discrepancy is mainly attributed to the irradiation induced surface lateral stress in ion irradiated samples, which cannot be taken into account for the Oliver-Pharr method. After carefully considering this effect by the finite element method in simulating the load-depth curves, both the Young's modulus and yield stress of ion irradiated samples agree well with those of neutron irradiated samples. This study reveals that by the combined method of nanoindentation and finite element, the mechanical properties, including the Young's modulus, yield stress and hardness, for neutron irradiated SiC can be reasonably evaluated by MeV heavy ion irradiation.